During regulation ice hockey at full strength, each team has six players on the ice: three forwards, two defencemen and one goaltender. Therefore, the standard answer is six players per team.
The three forwards are a centre and two wingers, usually positioned as a left wing and a right wing. The two defencemen protect their own end and help move the puck forward, while the goaltender guards the net. Teams constantly rotate players through line changes, so the six players on the ice are only one unit from a much larger roster.
The phrase “during regulation” means normal play, rather than overtime or a shootout. In the NHL, regulation consists of three 20-minute periods. A standard game has six players per side, but penalties can temporarily reduce a team’s strength; a team killing a penalty may have four or three skaters, while the opponent has a numerical advantage.
The goaltender is included in the six. That is why “six” is correct even though people sometimes count only the five skaters. A team may also pull its goaltender for an extra attacker, creating a temporary six-skater lineup.