There are lots of different terms used in guiding, which are useful for people who’ve been involved for a long time but can be confusing for new volunteers.
Here are explanations for the most commonly-used terms:

4: A peer education initiative. Young people are trained as in4mers to facilitate discussion of topics such as bullying, stress management, sexual health, eating disorders and binge drinking.
Adviser: trained adult volunteer with special responsibility for a particular area of activity.
BIG GIG: Pop concert held once a year for Guides.
Brownie Adventure: The activity programme for Brownies.
Brownies: for girls aged seven to ten.
Brown Owl: The informal name often used by Brownies to refer to their Leader.
CC: County Commissioner.
Co-ordinator: trained adult volunteer with special responsibility for a particular area of activity.
CHQ: Commonwealth Headquarters.
Commissioner: An adult volunteer responsible for the management of guiding within a defined geographical area usually a District, Division, County, Country or Region.
DC: District Commissioner.
District: Group of units, covering all age groups, which join together to provide a support network for Leaders and to organise events for girls.
Div Com: Division Commissioner.
Go for It: A resource aimed at the Guide section, providing programme ideas for Guide patrols.
Guides: for girls and young women aged ten to 14.
Guiding Star: Guiding Star is an exclusive X Factor style competition for ten to 25-year-old members of Girlguiding UK.
Leader: An adult who has completed Girlguiding UK’s Leadership Qualification.
Leadership Co-ordinator: volunteer with responsibility for the Girlguiding UK Leadership Qualification in your area.
PRA: Public Relations Adviser. PRAs inform people in their areas about guiding and how it is changing using the media.
Project 50K: a project that aims to improve ways to retain and recruit volunteers.
Project Streamline: a new initiative that aims to help every level of Girlguiding UK improve the way it manages information about its members.
Project SWITCH: Lottery-funded project aiming to take the opportunities available through guiding into a more diverse range of communities.
Rainbow Jigsaw: The activity programme for Rainbows.
Rainbows: for girls aged five to seven. In Northern Ireland Rainbows are aged four to seven.
Rangers: sub-group of Senior Section.
Senior Section: for young women aged 14-25.
TACs: Training and activity centres such as Blackland Farm, Foxlease and Waddow Hall.
TG: Trefoil Guild.
Unit: group the girls meet in.
Unit Helper: adult who regularly helps run a unit.
WAGGGS: World Association of Girl Guides and Girl Scouts.
Young Leaders: sub-group of Senior Section. Young women, aged 14-18, who help out at unit meetings. Some, aged 16+, may be working towards their Leadership Qualification.