It's a 30 minute slot but usually runs a little over that.
We first chat about how life is going for a short while, then topics anywhere from job satisfaction, personal or teamwide improvement potential, specific products or technical issues, performance inhibitors, anything that is on our minds with respect to the job at hand really.
That's pretty much what mine are. Some off-top-of-head rambling that sometimes reveals larger-scale stuff because the manager has other context, some "perf this year is likely to focus on X, please do that" reminders, some "getting exhausted by X, would prefer to not do it, what numbskull even came up with this".
It's for stuff that doesn't tend to come up in other ways, because there aren't jira tasks for mood. We skip about half of them when nothing in particular stands out for that week.