There are Resident orcas which are the most commonly seen in the Pacific East. They travel in strong, cohesive family pods and eat mainly fish but on occasion squid. They are creatures of habit and visit the same locations continuously.
The next are Transient and their distinctive quality is their diet, they eat mainly marine mammals, such as sea lions and sometimes they even feed on other whales. They travel in smaller groups from about 2 to 6 and they don't have such strong, persistent family bonds as other species of orca. They are also referred to as Biggs killer whale (because of Michael Bigg who discovered them) which is beginning to replace the transient label they currently have.
Lastly there are Offshore orcas, discovered in 1988. They travel much further than the other two types (as their name suggests) and have a diet of mainly schooling fish. They can travel in groups of up to 200 but the average is 20 to 75. Not as much is known about their habits, but they are known to be smaller than the other two types and female offshores have a more rounded dorsal fin.
2. Orcas have different vocal sounds - just like we have languages!