I’m not going to contribute original content on this matter because I’m no expert. I’m just going to summarize what I’ve understood and extract the information from a site that I find very useful. I would recommend this site to those who are keen to learn more on photography, or simply just want to know what the heck are those notations and functions in your digital camera and get the best out of your gadget which I’m going to do on my JitChak.

Auto Mode

Self explanatory! Your camera will use its best judgement to select shutter speed, aperture, ISO, white balance, focus and flash to take the best shot that it can. This mode will give you nice results in many shooting conditions. However, to get even better results under auto mode, choose the right preset mode. The ones described below are the typical functions that can be found in the digital camera nowadays.

Potrait Mode

Your subject becomes centre of attention while the background is out of focus. Your camera does this by selecting large aperture (see below) which keeps background out of focus. Best for photographing single subject in close range (not too close though). If you want to go very close as to snap a pimple use macro mode.

Macro Mode

As mentioned, this mode is for close up picture. Great for taking text, insects, flowers and small objects. Focusing can be tough at this range (2-10cm) so you’ve got to find the right angle.  Don’t go too close, but try zooming instead. Site suggest parallel, though I’m not sure what it really means. Often than not, don’t use flash taking close-ups or your objects will be burnt out (eg: reflection too strong)

Landscape Mode

Opposite of potrait mode. Camera sets to small aperture so that scenes/background will be in focus. Best for capturing shots with wide scenes or points of interest at different distances. Perhaps can use slower shutter speed (see below) to compensate for small aperture.

Night Mode

Camera sets to Slow/longer shutter speed for shooting in low light situations to help capture details of the background with the help of flash. It’s normal that the background is blur under low light. However it’s also fun to take such shots – especially when there is a situation with lights behind your subject as it can give a fun and experimental look (great for parties and dance floors with colored lights).

Action Mode

For photographing moving objects that is usually associated to sports, moving vehicles, kids and pets/animals. Camera sets to fast shutter speed in attempt to freeze the action. Suggestion by site is to pan of your camera along with the subject and/or by attempting to pre focus your camera on a spot where the subject will be when you want to photograph it.

Panaromic Mode

Great function to snap wide scenes. Suppose if you want to snap a scene too large to fit into one shot, you can take succesive multiple shots (usually up to 3) and your camera will ’stitch’ them up as one. Great for natural hill scenes, stadium, convention, etc.

Snow & Sand Mode

For tricky white/bright scenes. To capture details in this setting, use this mode.

Fireworks & Sunset & Sunrise Mode

Self explanatory!

Semi Auto Mode

Aperture Priority Mode (A or AV)

You set the aperture and your camera sets the other settings (shutter speed, white balance, ISO etc).Aperture priority mode is useful when you’re looking to control the depth of field in a shot (usually a stationary object where you don’t need to control shutter speed).
Bigger aperture (smaller number), more opening in camera, lower depth field, lesser sences in focus (remember potrait mode?) but more light in and camera will set higher shutter speed.
Smaller aperture (large number), smaller opening in camera, higher depth field, more scenes in focus (remember landscape mode?), but less light in and camera will set lower shutter speed.

Shutter Priority Mode (S or TV)

You set the shutter speed and your camera set the other settings. This mode is useful when you want to control over shutter speed to capture fast moving object (remember action/pet/kids mode?). You might want to choose a fast shutter speed to freeze the motion. On the flip-side of this you might want to capture the movement as a blur of a subject like a waterfall and choose a slow shutter speed. You might also choose a slow shutter speed in lower light situations.

Program Mode (P)

Program mode is full auto mode but gives you a little more control over some other features including flash, white balance, ISO, red eye etc.

Full Manual Mode (M)

Full control over your camera and need to think about all settings including shutter speed, aperture, ISO, white balance, flash etc. It gives you the flexibility to set your shots up as you wish. But of course, I seldom do that since I’m no pro. I use program and preset mode the most.

ISO – the measure of a digital camera sensor’s sensitivity to light

Lower ISO number, less sensitive your camera is to light and the finer the grain (crispier). Low (100) ISO is okay for bright place. Can set faster shutter speed and smaller aperture. You’ll get a relatively crisp shot.
Higher ISO number, more sensitive your camera is to light but at noisier shots (less crisp). Set high ISo when it is dark, and you want to capture action scenes. Set slower shutter speed and larger aperture to get more light in but again, higher ISO more noise. Sometimes you would purposely want noise – up to your liking. Play with higher ISO in situations for eg: indoor, concerts, art galleries, birthday parties (candle blowing moment in dark settings – try not to use flash but higher ISO).

Aperture - the size of the opening in the lens when a picture is taken

I think you get the idea from above description.
Big aperture (small number) good for potrait and close ups. More light in, can set higher shutter speed, lower ISO and you’ll get relatively fine crisp picture.
Small aperture (large number) for scenic view, distant picture. Lesser light in, so flash might be good. Set slower shutter speed and higher ISO but check noise level though.

Shutter Speed - the amount of time that the shutter is open

Also, I think you are clear in this already.
Faster shutter to capture image instantly. Useful for moving objects (sports/pets/kids/dancing..etc). Usually associated to lower ISO and bigger aperture (unless you use manual mode because semi-auto changes the other two when you set shutter speed)
Slower shutter speed is good for still image in darker conditions (to get mroe light in). Usually associated to higher ISO and smaller aperture (unless you use manual mode because semi-auto changes the other two when you set shutter speed)

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Hope you find this useful! And do make use of the functions in your digital camera, otherwise they’ll be a waste. They are there for a purpose. Happy exploring!

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ps: if you find information above contradicting to your understanding and findings, please let me know.