It involves learners getting up and talking to all the other members of the class.
Example
The group are practising using the present perfect for experiences. Amongst the group there are learners who have to:
find someone who has been abroad
find someone who has eaten something really strange
find someone who has done a bungee jump
In the classroom
This is a very versatile activity, which can be adapted to almost any language aim. For example, learners can practise multi-word verbs (‘Find someone who has fallen out with their partner') or character vocabulary (‘Find someone who is a lone wolf').
Further links:
https://www.teachingenglish.org.uk/article/activities-first-lessons-1