So a lot of it comes down to grip and arm action. The grip for a slider is very tight with the index and middle finger pressing down hard on the seams. The difference between a cutter and a slider comes down mostly to grip, which results in differences in velocity (cutters tend to have higher velocity) and movement (sliders tend to have much more lateral movement and depth).
For fastballs, the difference between a 2-seam and a 4-seam fastball is again the grip, to which their names allude to how many seams of the baseball are held. A 2-seam fastball is thrown with armside run, meaning it moves in the same direction as the pitcher's handedness (centre-right for RHP, centre-left for LHP). A 4-seam fastball is your prototypical "straight" pitch, generally it also tends to have some natural movement (either a slight cut or a slight run) depending on the pitcher, you usually don't watch your 4-seam to be too straight because major league hitters are really good and will lock in on it easily.
A split-finger (commonly called a splitter) fastball is a pitch that is held with the index and middle fingers held like a V through the seams, it acts much like a changeup in that it is thrown with the same arm action as a regular fastball and the velocity difference between it and the fastball is significant enough to keep hitters off balance. A good splitter will have substantial downward movement and sometimes will have lateral movement, in which it will look very similar to a circle-changeup (a pitch where two fingers form a circle around the side of the baseball).
I'd recommend looking up the different grips and more information on each pitch.