".F0" will be a name given to either a pin function or a port bit number. You should search in the ".inc" files which are probably listed at the top of the program and read their contents so see the equivalent pin number it refers to. For example, it might equate to PORTB.4 meaning bit 4 of PORTB.
The 'if' ststement is true if the value is anything except zero and the only alternative is '1' so it says "if the pin called F0 on PORTB is equal to 1 run the following code".
Actually, if you are coding in C, you may want to reference the device specific header file, for example p16f877a.h, rather than the Assembly INC files.