How exactly did people lose money in FTX?

Hello, I’m listening to the Spellcaster podcast and trying to make sense of what happened with FTX.

If FTX was an exchange, why or how did people lose money? Were they using their FTX account as a wallet instead of something like metamask? Maybe they just left their crypto balance on the exchange? I’m just genuinely trying to understand because it’s not clearly stated anywhere I look.

By the way, Spellcaster: The Fall of Sam Bankman-Fried is an excellent podcast if you’re looking for something to listen to. It’s very interesting and well done!