I see that some people have already answered you, but I wanted to also add the following: bandwidth on Steem will be changed to another system in the upcoming Hardfork 20 update. After this there will be no bandwidth, but rather a Resource Credit. You can read more about the new, upcoming system is this post: https://steemit.com/bandwidth/@steemitblog/blockchain-update-2-hf20-progress-and-bandwidth-changes