What would return if you sent a string value in parentheses next to another string

Im reading some psuedocode and im really rusty/not very knowledgeable on programming. In a funtion though its asking what would return for something like "return String2(String1)" where say string1 is dog and string2 is cat.

Or another example "String3 = String2(String1); return string3;". What would it show?

Just asking because i cant seem to wrap my head around this without that info.