Scrum-half
The scrum-half feeds the ball into the scrum and, all going well, will collect it when it comes out and start the attacking phase of play.
They wear the number nine in the starting XV.
Scrum-halves are often the smallest players on the field and must be agile both physically and mentally to make quick decisions and set up attacks.
Fly-half
Often the glamour player, the fly-half is central to a team’s attack and will usually direct play and issue tactical instructions.
They are also usually the team’s goal kicker – when the ball comes out of the scrum it will often be passed to them to kick, either for goal or to set up an attack.
In the starting XV, they wear number 10.
Centre
Each team has two centres in their starting XV – the inside centre, nearest the scrum, and the outside centre.
These players wear numbers 12 and 13.
As the name suggests, centres play in the middle of the pitch and must be good at running in attack as well as strong in the tackle against opposition backs.
Wing
There are two wings in a rugby team who in the starting XV wear numbers 11 and 14.
The left wing and right wing, as the names suggest, line up on the far sides of the pitch to provide speed and width to their team’s attack.
They are usually the quickest players and should provide the main source of tries.
Full-back
A full-back wears number 15 and is often positioned well behind their team-mates when lining up on the field.
They do this to catch high balls kicked by the opposition team and to provide a last line of defence should the opponent break through the main defensive line.
The full-back is also expected to support in attacks and start moves too, so must be exceptionally quick and physically fit.
Ellie Kildunne, England’s world player of the year, plays in the position for the tournament hosts.
This article is the latest from BBC Sport’s Ask Me Anything team.