Celery Blanching

I am unsure what the best way to blanch celery, anyone have any ideas?

I found this info on a web site and thought it might be helpful.
The celery should be ready for harvest in approximately 4-5 months from planting. However in order to give the stalks a good taste and a white complexion, cover the stalks 1 month before harvesting.

I am a bit new at growing vegetables. Always wanted to try growing celery. I am unsure exactly what is meant by blanching. Can anyone fill me in on this?