oe-c oe-a

What are they? I read somewhere theres one for v3.40 what would it do to my psp?

Sorry

but to reach an OE (Open Edition) firmware, you need to be at 1.5.

an OE Firmware has all the functions of the base firmware, but it also adds the homebrew powers on 1.5

you can't run any homebrew on 3.11 and up.

The letters after oe are the revisions (updates) of that firmware it goes in order of a, b, c. 'A' being the first release, 'C' being the latest release. But as Supashay stated already you need to be at 1.50 firmware to reach 3.40 oe-a, or at least a firmware that is downgradeable to 1.50 which would be 3.03 and under. So your pretty much stuck for the time being until a downgrader is made for 3.40. Unless of course your interested in purchasing a mod chip, or a motherboard with downgradeable firmware on it.

wow but how about the SE version what do they do

See is just an older version (Special Edition)

The letters mean nothing, they are just acronyms.