a (traditional) round robin---each person who is participating in the group creates a block---which will be the center of their quilt- then they send their block to the next person on the list who adds a border around it- and sends it on to the next person---each person adds a border- passes it on---when it gets back to you it has grown- by how ever many borders===
some robins have specific rules- as to the border added- such as first border - triangles, second border applique, third border squares, ect---
some robins do not specify that but many have size requirements---such as 6" borders- or 4" borders-
some robins let it always be the choice or the person making the borders.
some robins travel around the world (can be quite expensive to participate in due to shipping/insurance costs) some each person adds extra fabric- some no fabric travels with it-
there are variations such as row robins (where each person makes a row to go with the original row theme)
or a grid- where you fill in a space on a grid, block robins where each person instead of adding a border around the original block just makes another block to attach somewhere---many different variations- but the original is the borders around
if you are going to give one a try- read the *rules* and make sure you understand---the requirements, the costs involved- the deadlines (they have specific time frames for each border) if you have a sewing/quilting group in your area, or a lqs you frequent perhaps you could get involved in a (local one) before commiting to a (long-distance) one...
in the 10 years i have been participating in round robins there has only been once that i was disappointed with my finished quilt--all the rest of them have been absolutly spectacular!!! but read and understand the rules before jumping in it is a commitment===that can last 6-8 months or longer-depending on how many people are in the group.