A warband is the equivalent of a freep fellowship with the maximum of 6 players. A raid is a collection of players ranging from 2 to 24. The difference outside of numbers is utility. A raid has several tools such as Raid Assistants and Raid Targetting Assists to simplify leading and managing the raid. In general, a warband should always be converted to a raid to make use of these tools. There is no penalty to infamy in converting to a raid, given that the group size remains constant.
There are two ways to create a raid
To expand the raid
Raid assistants are added by right clicking on the portrait of a player, then pressing Raid -> Add Raid Assistant. The raid assistant can invite and remove members.
Raid Targeting Assists help focus the firepower of a raid and alleviates confusion of what the main target of the raid should be. The interface allows for a maximum of five targeting assists which are designated by right clicking on a portrait, then pressing Raid -> Add Raid Targeting Assist.
Members of the raid can enable on the Raid Assist window by pressing Social panel (O) -> Raid -> and checking Raid Assist Window.
For many people in the raid, it is unnecessary to see more than their group. To remove the information from other groups in the same raid, go to Social Panel (O) -> Raid -> then uncheck Show Vitals for all members except those that they wish to display.