Running and active queries, also currently waiting queries.
Using DMV like sys.dm_exec_query_stats to analyze queries.
📝 IO
IO related diagnostic queries.
📝 Locking
Locking and blocking related diagnostic queries.
📝 Memory
Memory related diagnostic queries: buffer, plan cache, query memory.
Query Store Management and information.
📝 Sessions
Lists and finds sessions: by host, in a specific database...
📝 tempdb
Tempdb related diagnostics queries.
Wait stats related queries.