Under Exposure / Correct Exposure / Over Exposure.
With all these three you Requires getting the right amount of light to the sensor / film to get a good image.
learning to estimate how long you need to exposed light to your sensor.
shutter speed is normally measure in fractions of a second e.g 1/30 1/60 1/125 1/250 1/500.
with a faster shutter can reduces motion blur but admits light.
For catching blur pictures you will need a slow shutter speed with a longer Exposure time. It will be best for to experiment doing it with your camera.
If you are catching Fast moving objects like Cars you will need a faster shutter speed with a shorter exposure time to catcher a clear image of a car etc.
The aperture is to show much light go throw the lens.
the f-number is the focal length from the camera to the object.
a big f-number which light passes is now greatly reduced.
for more light you need a smaller f-number.
Depth of Field
The Depth of Field is pointing your camera to a person or a object and getting a clear image of the person and the back ground.
Clear Back ground
By using a small aperture and a large depth of field makes the back ground clear.
Blur Back Ground
And by using a large aperture with a shallow depth of field will make the back ground go all blur.
The Focal plane
Focal plane is the distance from lens of the camera which that the sharpest focus is attained.