The exposure triangle are the 3 components that make up a good and well exposed photo .
Aperture :
Aperture is how big or small the iris is , it is measured in f-stops such as 2.8 , 4 , 5.6 , 8 , 11 , 16 and 22 the lower the aperture eg; 2.8 the bigger the iris will be, this means that you will get a shallow depth of field what this means is that you will get a slightly blurred background on the other side the higher the aperture like 22 the smaller the iris will be , this means that you will get a great depth of field what this means is that all of your photo will be sharp.
This picture has got an aperture of 4 , this is why it has got a shallow depth of field and thats the reason it has a blurred background
This picture has got an aperture of 15 , this is why it has got a great depth of field and thats the reason its background is sharp and in focus
Shutter speed
Shutter speed is the time that your camera shutter is open, its basically how long your camera spends taking a photo.It is measured in seconds such as 30,15,1,1/10,1/30,1/250 a high shutter speed such as 30 will allow you to show lots of movement such as water flowing whereas a low shutter speed will allow you to quickly capture the scene as if it were frozen this would be best if you need to quickly capture somthing an example of this is in sport as you do not want ghosting and random thing noving around in your picture.
Iso
Iso Is is essentially the feature that allows you to either brighten or darken a photo , a low iso such as 100 will give you a darker picture whereas an iso such as 12000 will give you a much brighter image however having a higher Iso also has a drawback being that your image will end up being more grainy.Iso is just measured in numbers a low iso means a darker image and a high iso means a brigher image.You typically want to use a high iso when your in a dark environment and you want to use a low iso when your in a wel lit environment