Play-in tournament format

I’ve been trying to follow the NBA playoff race a bit more this season, but the Play-in format still confuses me sometimes. I get that the top teams go straight into the playoffs, but once people start talking about 7th to 10th place, one-game chances, and teams “falling into the Play-in,” I lose track. Last night I was checking standings with a friend and we couldn’t agree on why some teams were still considered dangerous even outside the top six. Is there a simple place that explains how it works and why it matters so much late in the season? I usually look for short breakdowns rather than full statistical deep dives, because I mostly want the big picture.