A tool assisted speedrun (commonly referred to as a TAS) is a sequence of inputs by a human with the help of either 1 or multiple tools that completes a level/map in the fastest way possible. With the computer you can use anything like slowing down the game or bruteforcing to complete a certain map or level very fast.
What is bruteforcing?
Bruteforcing is a thing to make your life easier. Instead of playing a level or a map for like 500 hours to get that singular good run you can just get a computer to do that! With bruteforcing you can supply a tool with inputs or even a replay file and it will try thousands of options a second to get that perfect run even faster.
I even have some pages dedicated on how to TAS in a game called Trackmania