If you've for example a large conference room with let's say 90 clients you'd put in 3 APs.
Then add this 3 APs in a load group and the controller attempt to steer the clients equal to the 3APs.
– Provide same SSID’s– Preferable Line of Site (LOS) between each AP
– Deployed on multiple channels with overlapping coverage
– Clients in the area are able to associate with any of the AP’s