If two teams are tied after the end of the second half of the game, they will enter overtime. The first stage of overtime is two five minute overtime halves. If teams are still tied at the end of the overtime period, the game will enter sudden death. Sudden death is a period where teams play until the first goal is scored. Once a team scores a goal, the game is over and that team wins.
The full overtime protocol described above are not implemented in every tournament. Many tournaments will only implement overtime in the final games, and will often skip the two overtime halves and immediately enter sudden death.
This Elite Womens gold metal game in Quebec City, Canada in the 2018 World Championships has all the ovetime steps. There is first two five minute ovetime halves, then sudden death.