What did light carriers do in wartime fleets?

Did United States and Royal Navy light carriers have different doctrines in the Second World War?

Not fundamentally: both augmented fleet-carrier operations, although their hull origins and ultimate aircraft capacity differed.

Both fleets used light carriers as force multipliers that filled gaps when full fleet carriers were unavailable. American CVLs grew from cruiser-hull conversions, while British light fleet carriers grew from a very different design lineage, including the aircraft-maintenance ship concept behind HMS Unicorn. Their missions still overlapped: adding flight decks, aircraft, and presence to fleet operations.