All the settings below will also be explained in your camera manual.
Camera does all settings. The camera works out the depth of field and speed and iso. It normally delivers a guaranteed shot.
Av – Aperture Priority
You set the depth of field and iso , camera sets time
This changes the Fstop value , remember the lower the value the more the lens opens giving more light but a shorter focal distance
Average setting is f8 , portrait (f8) and landscape (f11)
The range of fstops you can use will depend on your lens
Tv – Time Priority
You set shutter speed ( length of time the shutter is open) and iso , camera sets aperture
Good for sports and wildlife and birds in flight.
The longer you leave the lens open the more movement you will record
So a moving sky in a landscape would be slow 1/30 .
Whereas a bird in flight would be fast 1/1250
Iso—leave on auto to start off with
The greater the ISO the better the light level recorded but it is a digital enhancement so too high and your picture will become grainy due to noise
You set aperture , time and iso so you need to understand how these controls work together and affect the picture before using it
These are predetermined values that would typically suit that type of picture(scene) and are a step up from auto before doing the settings for yourself