Shape

Shapes are obviously the shape of a part. There are three different shapes, cylinders, spheres, and bricks.

Brick
Parts are usually found as bricks. Bricks have 6 flat faces, and will usually have studs on the top surface.

Cylinder
A cylinder is commonly found as wheels on a car or a truck. They are often used for things that spin, because they have a round part. To create something that spins, put hinges or motors on the flat sides of the cylinder.

Sphere
A sphere is also used often for spinning things. But you can also CFrame it to create hills or caves or anything like that.