The first 1-2 numbers is the generation of Nvidia gpu. The latest 4 generations are 10xx, 20xx, 30xx, and 40xx. The last two numbers differentiate between gpus within a generation. The higher the number the better the gpu, xx70, xx80, and xx90 are common. So the newest gpus that Nvidia are putting out are the 4080 and the 4090, their newest generation and top two performing cards within that generation. In-between generations they usually release a ti variant of the card (3080ti) which is a moderately better version but not a new generation.