what will happen if server reach max threads

When i study network and server knowledge. I'm curious about one question

Is user requests and server threads a one on one map?

What if there are 1001 users requests simutaniously and linux server has max threads as 1000?

I don't know how to do experiments for this. So here is my specific question

if a web server set its max threads as 1000, and there are 1001 users who are downloading a 5GB file. what will happen to the last user? wait and timeout? or just hang there until user send data to him