The first line of the function declaration defines how the function is identified and addressed. This is called the function's signature. The signature specifies the name of the function, what values it can take in through function parameters, what (if any) return value it outputs, and any other pertinent information about the function through the use of function specifiers.
The most basic function signature begins with the function keyword (special event functions begin event keyword instead). This is followed by the optional return type of the function, then the function name, and then the list of function parameters enclosed in parenthesis.
From the example declaration above, the signature portion is:
function byte GetTeam(Pawn PlayerPawn)
This signature is for a function named GetTeam that takes in a reference to a Pawn and returns an byte value (which you can guess by the name of the function represents the team of the Pawn that was passed in).
Functions can also have certain attributes determined by the use of function specifiers in the declaration. These generally precede the function (or event) keyword in the signature, though some must be placed in other locations.