Juan,

This means the PIC you selected has

8K program memory - u can write code a little smaller that 8K size.

368 bytes of inbuilt RAM bytes(in addition to the Special function registers which map into the same ram space). Microchip designers calls this general purpose RAM bytes.

256 bytes of inbuilt EEPROM memory. You may store your program parameters which are not supposed to get erased when the chip is reset.

By the way, PIC 18F87X are more wonderful chips from microchip. They have +75 assembly instructions even!

Achu