What is osc bank?

Hi I recently learned about osc but I can not find what exacly is the role of bank in osc?
Thank you

Here, a bank is a term from the MIDI universe.

The bank size is the number of tracks or mixer-strips that you can control at the same time on a given control-surface.

e.g. if you have a mixer-desk with 8 faders, you’d use a bank-size of 8 (and can then switch to the prev/next bank to control all tracks if there are more than 8); or you could use a bank-size of 7 with a fixed master-fader on the 8th fader.

As for the relation to OSC, please see http://manual.ardour.org/using-control-surfaces/controlling-ardour-with-osc/osc-control/

Also note that as bank size defaults to “0” or use all strips. It can be safely ignored if you have no use for it.