This one of the methods under the Tech Auto-Assign feature.
In the Round Robin method, the application assigns requests equally to all technicians, and follows a circular order.
Let's say, you have 3 techs (Tech 1, 2, and 3), and 10 requests are in queue. In the Round Robin method, Tech 1 will be assigned 4 requests while Techs 2 and 3 will have 3 requests each. Now if 2 more requests come in, Techs 2 and 3 will each be assigned 1 request. Requests will be assigned, regardless of whether the techs are still working on open requests.
The Tech Auto-Assign feature also takes into consideration the Groups and Sites associated with the techs.
Let's say tech 1 is associated to HR and Admin while tech 2 is associated only with Admin. If there are 7 requests created, of which 4 are under HR and 3 under Admin, tech 1 will be assigned all of the HR requests, whereas the Admin requests will be assigned equally and in the circular method. That is, tech 1 will be have 2 Admin requests and tech 2 will have 1 Admin request assigned.