Part

A Part is a group of triangles that when rendered in the Client's renderer appears as a Brick, Users can use these bricks to craft a Place or Model.

The main Class of a Part is the Base Part. they appear Lego block like.

Base parts can only be used to build, nothing more.

The secondary Class of a Part is the Mesh Part/Special mesh. These allow you to have a custom polygonal structure, instead of the classic brick shape, simply insert a .mesh file, or use a link to one. You can also use a texture, for textures, you can upload .png, .jpg, or other image formats, or use a link. 

You can also set custom shapes, Ball, Cylinder, etc.