What are the various smiley faces to the left of the player faces when the scores are shown?
None of these are stupid questions

I've always wondered about the smiley face thing too.
Yes, the options can seem very confusing for new players. Should pick up alot of stuff fairly quicky.
Bots always have 0 ping.
Team games usually/nearly always have red or blue team players.. so when you see your player name in the scores and beside a bunch of blue players.. then shoot red

A chat icon appears above a player when they are typing.. like this --> ; D

That doesnt mean they want to befriend you.. but its polite not to shoot them until they have finished typing (unless its a free for all game with lots of players)
Never assume a players name is who they really are. I shot George Bush right in the ass last week but not 100% sure it was really him.
circle jumping is something that only a player who is very confortable with mouse movement would be find useful. I know great players who learn much later how to do that stuff.