It affects the current turn and the next turn. This could affect the same player twice if they have two turns in a row, or it could affect different players. In a multiplayer game it affects exactly two turns, not a full round of turns.
Doesn't skip the Combat Phase, just renders creatures unable to attack.
Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keywords are activated abilities and will have colons in their reminder text.