checks are results of night actions (usually alignement or at least role indicative, in this case both)
red checks mean you found scum
of course lying is part of the game, so anyone can claim a fake check
selfpressing is when you vote to save your skin rather than your highest scumread (after you got voted up). Its against anyones wincondition to get lynched (with some exceptions, but even then you should vote as if it werent one). As town you are the only one you can truly know to be town, as scum survival is even more important, as you only have 1 more teammember to grab the win.