That’s entirely the unfiltered combat log, unless another player spotted you and had his addon alert other users. If you have certain Auras up, it will flag you into the unfiltered combat log. Some buffs will even spam you into it. The log can be very spammy. I don’t like this either.
The API does not allow for players to get the location of other players, unless they are in your raid or that the other player has broadcast their location.
The API does not provide health status, mana status, level, or class through the combat log. It only does this after a player targets or mouseovers you. However, addons can document your last known status or guess these things based on the information provided by the API.