No, you would not be withdrawing it at the moment, but investing it back into Steemit. It's still available for a future "power down" if you need.
I've written an article on it, though I will improve it later in the month when I celebrate the end of my second month here on Steemit.
I hope the article helps.
https://steemit.com/steemit/@viking-ventures/steemit-for-newbs-part-2-bandwidth
Plus one with more details on voting power and how your steem power affects it.
https://steemit.com/steemit/@viking-ventures/steemit-for-newbs-part-3-voting-power
I'm now at about 27 SP - still quite low, actually, but I'm not having so much trouble with bandwidth now and my vote is more often worth something (at least my penny...) My understanding, from more-experienced bloggers, that I should be aiming at 50 to 100 SP minimum. After that, it's really up to me and how much voting power I want. (Worth investing back as long as the cryptocurrencies are down so much.)
I really hope this helps. (Yes, the whole thing is really confusing - I've even seen "whales" explain the bandwidth thing in a way that doesn't fit my observations.)
Best wishes!
RE: i just upvoted someone and their balance went DOWN 1 cent !!! ???