Why does "A" get added onto the front of names in C++

I’m just wondering what the purpose of the A is. Such as the A in ASprintCharacter.

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Thank you

Classes that inherit from UObject are prefixed by U.

Classes that inherit from AActor are prefixed by A.

Classes that inherit from SWidget are prefixed by S.

Check more at Coding Standard | Unreal Engine Documentation

Thank you for clarifying!