In my case, it's a mixture of life wiki, personal project wiki, videogame wiki, and journal (not daily, but more for a few significant days).

Like, there's this cluster with all the people that I know, pointing to their respective communities, and who participated in which annual social gathering (which have their own articles with pictures and videos). With one (usually rather empty) article per person, I can just link to them from other relevant places.

Then there are all my (software) projects and generally intellectually interesting stuff I thought about, which I wrote down over the years (which took me a few weeks to digitalize/find/sort once I got my hands on obsidian).

In terms of video games, it's either the knowledge/realizations I made or rough copies from some online wiki articles. Considering my internet provider is horrible and unreliable, having an offline source can be really nice sometimes.

In general, it's really useful to support my shitty memory. Having detailed descriptions of what I've made or what happened just makes it easier to re-experience certain moments.