I'm XahKai. When your submitting a run, what does In-Game Time Mean? I'm sorry if it is a dumb question, I just really need to know

IGT (In-game time) means a timer or a clock that exist in the game itself, and you submit the final time shown on that clock. For example: https://www.speedrun.com/a_pirate_and_his_crates

RTA (Real time attack) means the time it took from start to end frames of a run, while counting all the time in the middle like pauses and loads. Used when the game doesn't have an in-game timer, or when it's inaccurate, or other reasons.

It's up to the moderators/community of each game to decide how to track the times on the game, with IGT or RTA. There are also leaderboards where you can submit both times.