When I was still planning to buy a PSP, I searched for everything about PSP like comparison reviews between the fat(old PSP) and slim(new PSP), tech specs and prices. One important information I found about the PSP is it’s ability to use the Firmware, a firmware(commonly abbreviated as “FW”) is a software that runs the PSP, it functions the way like an OS does(FW is for PSP and OS is for PC). Many Firmware versions are released from time to time and labeled by numbers(the latest as of now is the FW version 3.73). The PSP firmware features an easy to navigate graphical user interface called “XrossMediaBar”(abbreviated as XMB) which is composed of main icons spread horizontally and sub icons vertically.
an example of the firmware XMB GUI:
There are two types of FW currently available, first is the Official Firmware(abbreviated as “OFW”) and the Custom Firmware(abbreviated as “CFW”).
OFW is the one that sony officially uses and releases. It has the standard features of the PSP, each update contains security patches that prevents the use of homebrew applications(unofficial applications).
CFW is the winning choice in my opinion, CFW is similar to OFW, only better! it is a modified version of the official firmware, developed by team M33, a group of programmers. It allows the use of homebrew applications making it possible to play ISO games extracted from the original UMD format as well as running emulators from many platforms(so far I’ve seen MAME, snes, ATARI, GB/GBA and PSX) and still perform what the OFW can offer. My PSP has the CFW version 3.71 M33-2 and I really enjoy using it.