Support ships concentrate mostly on suppressing enemy fleet capabilities with Electronic Warfare, and sometimes enhancing friendly ships. Support are mostly composed of Combat Recon Cruisers, Force Recon Cruiser, Electronic Attack, and Logistics making them great counters for other support fleets while helping their own fleet.
There are many ways to perform the Support role in fleet. This role generally does not receive praise, or appear on killmails but all fleet fights would be lost without them. These are the unspoken heroes, the watchful guardians, the silent protectors. You're basically Batman.