Sevens is a game where (obviously enough) you play with only seven players aside instead of the standard 15. Scrum and lineout numbers are reduced accordingly. It is a much faster game than standard Union if only because there are fewer players to make tackles and therefore fewer breakdowns/phases. The ball also tends to change hands less often. A standard game consists of two seven minute halfs, which is about as long as anybody can go at that pace without somebody's heart exploding. Aside from the changes in the number of players and time, there are only two changes from standard 15s. The first is that all kicks at goal, including penalties and conversions, must be drop kicks. You are not allowed to bring a tee onto the field. The other change is that after a team scores, it is the scoring team which restarts with the dropkick at midfield, rather than (as is the case with 15) the team which is scored upon.

union is 15 v 15. Sevens is 7 v 7. Sevens is a game more based off ball possession, its also a faster game because of the open space with only 14 players and the ref on the field. Also in sevens there is very minimal rucking.

15 vs 7. union plays two 40 minute halfs and 7's play two seven minute halfs.