What does RA1 stands for in PIC microcontroller?
Microchip lists any memory-mapped I/O as Special Function Registers.  So RA1 is bit 1 of the Port A Register.

In addition to the ports, which are accessed through registers PORTA, PORTB, PORTC etc., there are also tri-state registers (TRISA, TRISB, TRISC etc.) which set up whether a pin is an input (1) or output (0).

At least for the smaller PICs, Microchip also refers to its static RAM (which may be as little as 16 bytes) as General Purpose Registers (GPR).

The SFRs and GPRs are mapped into the same address space (i.e. the I/O ports can be addressed like RAM).