what does "flash recovery" mean? In the instructions for ClockworkMod Recovery for Galaxy S i9000, there is:


  Step 2. Flash Recovery.


I don't understand what this means. Which recovery to flash? How to do this? (With a USB cable, or it can be done by some manipulation with the phone alone, without connecting it to another computer?)
The general consensus is there's usually different partitions available:


system
data
cache
boot
recovery


When a guide says to flash "partition" where partition is one of the above, then that implies transferring the contents destined for the partition. The mileage will vary depending on the handset/manufacturer as not all of them actually have implemented partitions like the above.

Usually it can be done with using the cable plugged in and using fastboot.

For example: 

To flash a kernel onto the boot partition one can undertake it like this:

sudo fastboot flash boot boot_image_file.img


followed by:

sudo fastboot reboot


Likewise in the OP's case, its referring to the recovery partition.

sudo fastboot flash recovery recovery_image_file.img


I would be wary about using ROM Manager to do this for you without using a computer; Have got bitten by it, and found that it can sometimes, be incorrect with regards to using recovery i.e. ClockworkMod Recovery, it was so convinced that I had a very old version of CWM, when in reality, the latest was installed; end result, I messed up the recovery and threw away ROM Manager as I preferred to do it on the computer - less errors and that the human checking is in place.