The ICC's professional staff provides live online help, adjudication of abandoned games, and an active computer-detection team to ensure you won't have to play against computer-cheaters.
"decline draw" declines a draw offer, if one has been given.
Similarly, "decline adjourn" declines an adjournment offer,
and "decline abort" declines an offer to abort the game.
You can also decline offers in games simply by making a move.
"decline Fred" would decline a challenge from Fred, if Fred
has requested a match with you.
"decline" by itself will try to figure out what you mean
and do that.