That could be thoughts, things you're thinking about, thoughts about the past, the present, the future, thinking thoughts, or thoughts that are… rambling thoughts with specific thoughts.
The fulfilled guests sat back, sniffed, drank their coffee, laughed, tipped their cigarette ash on the floor, having missed the ashtray by a hair's breadth, gossiped, and refilled their glasses.
He meandered off into a long-winded reminiscence, but Harry had the distinct impression that Slughorn had not finished with him, and that he had not been convinced by Neville and Ginny.
Sometimes, they mumble or they ramble, they just don't speak with clarity and they may not have the charisma to get their idea across; so they are not charismatic.