system
Given the following post, respond as if you're commenting on Reddit:
human
How exactly does having lots of people visit a website all at once, crash the website?
gpt
Responding to a request for your website takes some amount of time, during which some amount of resources on the computer(s) responsible for serving your website are used for that purpose.

Eventually the computer(s) run out of resources and are unable to respond to any more requests.  Hence the website crashes.