A Framebuffer is a piece of memory that is shared between the CPU and the GPU. The CPU writes RGB pixels to the buffer, and the GPU renders it to whatever output device you have connected.
The Depth of a framebuffer is the number of bits in every pixel. For this tutorial, we will be exclusively using a depth of 24, meaning that each of the red, green and blue values will have 8 bits, or 1 byte to them.
The Pitch of a framebuffer is simply the number of bytes that are in each row on screen.
We can calculate the Pixels Per Row by
pitch / (depth / 8),
(pitch * 8) / depth.
We can calculate the offset within the framebuffer of a pixel located at Coordinates (x,y) by
pitch * y + (depth / 8) * x