When it comes to the most basic 3D theory, it's all about shapes in a 3D space using the coordinate system to calculate it's position.
All the shapes are built from vertices. A vertex have attributes like position, color, normal and texture. Position identifies it in a 3D space [x, y, z], color holds an RGBA value, normal is a way to describe the direction the vertex is facing and texture is the image that the vertex can use instead of a simple color.
The face of the given shape is a plane between vertices. For example, a cube have 8 different vertices (points in space) and 6 different faces, each constructed out of 4 vertices. Also, by connecting the points we're creating the edges of the cube.
The geometry is built from a vertex and the face, while material is a texture, which uses an image. If we connect the geometry with the material we will get a mesh.
[TO DO: add images, coordinate system, transformation matrix, projection, meshes, vertices, etc]