Include files can include other include files. This prevents you from accidentally including the contents of an include file twice, which would give you errors about a method being already defined.
On a side note, never name a variable int as this isn't a valid variable name in SourcePawn 1.8 or newer.
I've just been copying and pasting the same include stuff for about 4 years now not gonna lie to you. Thanks for the heads up though.