Steem is an open source blockchain where you can create uncensored content that remains forever. At first it was onlyformed by a social network called Steemit, in which you can monetize your content according to the votes of other users. After seven days, he receives the money, which can be Steem, SBD and Steem Power. Nowadays there are more apps in blockchain, for instance Bloque64 (Decentralized Hispanic news media), Splinterlands (trading card game), Dtube (platform to share videos) and more!
SBD is a secondary currency in Steem blockchain. Its value is linked to the usd and the calculations made in Steem are based on that value. It means that the money you earn in your posts (as long as it is in SBD), will be the same than to other posts with the same value, no matter the value of SBD in that moment. For instance, if you have 5 usd in SBD, you will receive 5 SBD even if it has a worth of 0.5 usd or if it is worth 10 dollars.
In case SBD has a value over 1 usd, your earnings will be higher than the ones that appear in the post. However, if it is less than 1 dollar, your earnings will be less.
But there is an internal mechanism that can convert SBD to Steem for the value of 1 usd, that takes a period of 3.5 days.
That is why SBD is considered a debt, and when this debt is over 9%, less SBD are received in posts and Steems increase until it is 10% or more. Then it is only received SteemPower and Steem.
* % is referred to the difference between the current all Steem value and the current all SBD value.
That is the reason why the result that is shown in the buying and selling section is not accurate when SBD is less than 1 usd. It would be accurate if there would not be the possibility to convert SBD to Steem.