Could someone please explain these 2 pitches?

Sliders don't break downwards much, but they have a lot of lateral movement. Sliders tend to "slide" in the direction of the pitcher's glove side. Sliders also tend to have decent velocity, they're about 5-10 mph slower than the pitcher's 4-seam fastball. Pitchers who throw good sliders tend to match up well against hitters who bat from the same side they throw from. This is because a good slider will break down and away from them, which makes it hard to judge how far they need to swing.

Cutters tend to be a mixture of a fastball and slider. They're about 2-5 mph slower than the pitcher's 4-seam fastball. A cutter is sort of like a slower fastball that breaks slightly towards the pitcher's glove side. This pitch can be used really well because it's almost a fastball with slight lateral movement. Mariano Rivera's primary pitch is a cut-fastball.

Sliders are curveballs but curve in the opposite direction.

Cutters are also called "breaking balls" - They drop downward as they cross the plate.