Message from C, C++ talks
I'm not an expert, but usually you work with vertex buffer and index buffer.
First is array of size n*3, where n is count of your verticles, and every three elements represent a vector coordinates [x1, y1, z1, x2, y2, z2, ...].
Second one is size m*3, where m is count of your triangles, every three elements represent indexes of vertexes from the first array [0, 1, 2, 2, 1, 3, ...]
There are also strips and fans that being encoded differently, but they are rarely used.