what exactly is PBC and would I want it for burning movies?

[hence]

or is PBC something used for slideshows, etc...?

[AntnyMD]

PBC, or playback control, enables you to interact with the menus and other remote control options available to you in the VCD2.0 spec. My guess is everyone wants playback control. I could be wrong.

[ktnwin]

Just my two cents.

Yes, PBC stand for playback control but it seems to work backward on the Pioneer DV-333 and DV-343.

Anytime I stick a VCD in my DV-333 player and hit PLAY, it shows "PBC PLAY" on the front panel display instead of the track number and the time. I could not interact much with my DVD player in this mode.

I accidentally discover another mode by NOT hitting the PLAY key but press a numeric key instead. The track and time are displayed as with a normal DVD disc. In this mode, all other remote control functions work as usual.

[d4n13l]

Amen to that.
I have a Pioneer DV-525. When I put in a VCD it comes up as PBC straight away and starts playing, but it limits certain functions as you say - I have to press a few keys for it to change into showing the time and chapters which also gives me more control.
My guess is though that you want PBC as every VCD I have ever played causes my player to display "PBC".