We need to understand one particular graph.
EV is a combination of shutter speed and aperture that can be used to measure the amount of light on the scene.
On the lower left corner the least ammount of light and the upper corner more light.
EV0 represents the light that will be properly exposed with f1 at 1s. If we increment the amount of light (upper right) will be EV1, EV2, etc.
The EV increments are the thin diagonal blue lines. As you increment a bit more to the upper right your ambient light on the scene, if you do nothing on your camera will be more and more overexposed.
So we need to interact with that diferent ammount of light changing our settings on the camera. f stop or shutter speed.
This graph represents the compensation we need to make on our camerea. So far so good?
AP & SP
The easiest examples are Aperture priority and Shutter priority.
On Aperture priority mode we define our diapgragm (red) and the camera, as we have more or less light just augments the shutter speed or reduces it.
And on the Shutter priority we define the shutter speed, and the camera adjust the aperture, as far as our lens allow it (blue).
Remember. Starting here you lose control on the aperture and the shutter speed This is what the modes starts to control.
A portrait mode, in theory assumes that we want some bokeh, this is a big aperture, but also that if we have a low shutter speed, we need a flash, so our image is not blurred. So it would be using the widest aperture to some extent. If the amount of light is more than our maximum speed, it starts to close the diaphragm. (It could include a red eye reduction preflash for example).
Sports mode is almost the same case, but for other reason. It does not care about the bokeh, but wants the fastest shutter speed. So it stays open the widest.
But It could think "Oh, I assume that (for example) 1/125 is enough. Probably the user wants something more deepth of field, let us start closing the diaphragm".
This 1/125 (hypotetical) is dependant on the focal length of the lens. If you have for example a 50 mm lens, it could be 1/125s, but if you have a 100 mm lens the sports mode could change that to 1/250s (light blue).
Landscape mode could be a little diferent.
It's priority could be focus. So its starts closing the aperture when it can to start focusing more and more.
Some other settings that could be affected
This modes could start making changes on some other settings, for example:
The metering mode; On a portrait it could asume that needs to expose right the center of the image, independendly of the background, so I supose they change the metering mode to center weight.
Landscape on the contrary could change the metering mode to matrix.
Soprts mode could start taking control on the ISO speed, if you have it on ISO 100 it could change to ISO 400 or 800 for example.
I thought this modes would leave alone the focus points. But both on Nikon and Canon they are on automatic focus points, they probably adjsut also the "auto tracking" autofocus modes.
Some settings also affect the sharpness, contrast and saturation of the processed image.
Newbiest mode, Auto and Green square
Here the program could think... "I have no idea of what a newbie user wants,
I will keep a minimum shutter speed before I pop the flash (a). Wait! Does he want to have more in focus? I will close the diaphragm (b) but what if he can not hold steady the camera? I will increase the shutter speed..."
And this goes on an on, untill a minimum workable diaphragm (c) where it could starts producing difraction.
You loose total control on the camera settings. This programs take in acount other factors, like focal length, but also activate some other like ISO Speed, the auto focus points, metering mode. All in Newbiest mode.
The aperture and shutter speed are decided for you. Simmilar to the previous graph. But it will not touch some other settings, like the focus point, the ISO speed or metering mode. You can still alter this initial decision of the camera.
(I feel this is a legacy mode. Back in the days of film cameras you could not change the ISO of an already loaded film, so it was fixed. In my opinion this mode should try to adjust the ISO before messing with the aperture, and try to achive a functional hand held speed, for example)
There are other modes, which I call.. WTHeck are this? A kid, a baby, a horse... I do not have a horse! You need to gess (or investigate) what the thoose mean. A baby? probably won't pop up a flash. Will a horse mode pop up a flash? and If it scares the horse? I do not know if a horse gets scared with a flash... I do not have a horse. Where is the puppy mode? I do have a puppy.
I call them newbies, because you leave to the camera the decisions the photographer needs to make. Of course someone could achive spectacular images with a totally automatic mode. But the point is to know the camera.
There are some graphs out there explaining how a particular camera or brand reacts to this light conditions on this P modes. But personally... who cares!
Just stick to AP or manual modes and learn how to exploit them.
Know your shutter speed limitations when you are holding a camera by hand and the situation you have infront of you, learn how to exploit motion blur, play with ISO speed and metering modes, choose your focus point and focus tracking modes.