Basically, if your psp has version 2.71 or lower when your buy it, you have the option of running homebrew on your psp. Currently, if it comes with 2.81 or above or you update it to 2.81 or above, you will have no access to any homebrew.
The way you access homebrew is by either downgrading your firmware back to 1.5, using a modified version of firmware 2.71 names 2.71SE, or loading a small piece of code on a normal 2.71 firmware named HEN-C.
People found a way to run homebrew on firmware 1.5 a long way back, and since then every so often someone has discovered and relased a way of downgrading more recent versions back to 1.5.
2.71SE and normal 2.71 with HEN-C running basically is like running firmware 2.71 with the homebrew access of 1.5, they are more recent developments.
Once your psp is at or above 2.81, you cannot go back to these options untill a new downgrader (possibly) gets released.
These firmwares (and the downgraders) use what sony call 'security flaws' (most of their updates are nothing more than 'security patches') to allow code not licensed by sony to run on your psp. The security updates are more about securing sony's buisness model than keeping your psp safe.
The most popular homebrew applications are probably emulators. These are programs that let you run games from other systems on the psp, eg: NES, SNES, Master System, Megadrive (genesis), Gameboy colour, GBA etc.
PSPVideo9 is the program I use to convert video for the PSP, there is a way it integrates with videora, but I have never used or even looked into videora so I can't help you with that sorry.
For dvd-PSP transfers there are some all-in-1 programs that are supposed to do it, I still rip my dvds to avi (divx) the old fasioned way with dvd-decrypter, dvd2avi, headac3he, gordian knot and virtualdub then just use pspvideo9 to convert to mp4 (psp format). When I buy a dvd it gets ripped to divx and put on my xbox's HDD, so I dont mind going to divx in between dvd and mp4 (psp).
There are plenty of better places to look for info on how to do it simply rather than getting me to explain the rather complex way of doing things I picked up years ago. Try
This Guide.
Check out the website I linked to in my previous post, look down the menu bar on the left hand side for all of the systems that you can currently emulate.
If you are lucky enough to get a psp with firmware under 2.71 and want more info on how to do things/where to look for instructions just give me a PM, glad to help.