Selection of compiler depends on various factors.
There are many compilers for different languages. Most notable programming languages are Assembly language and C language.
PIC Microcontroller family contains several types and it also categorized using length of registers. There are 8 bit, 16 bit and 32 bit type Microcontrollers and each does have separate compilers.
There are official and third-party compilers available for PIC Microcontrollers. Official compilers are developed and maintained by Microchip, the PIC Microcontroller manufacturers.