When more than one issuer offers tokens tethered to the same currency, for example, Bitcoin (BTC) we group these together. When you come across an asset with a [+] next to it in the Markets view, you can click to reveal all the issuers offering a version of that asset.
There are five different BTC tokens (at the moment) because five different entities are offering to hold your BTC in return for a credit on the Stellar network. This credit takes the form of a BTC token.
|The 5 BTC tokens currently on the StellarX marketplace (Nov. 18th 2019)|
If you buy or trade for a BTC token issued by one anchor, you can, at any point, redeem that token with the anchor for the equivalent amount of BTC on the Bitcoin network.
You can also trade that token on StellarX, and since different anchors offer different rates for the same asset, there’s an opportunity here for experienced traders. Please note that a BTC token issued from one anchor cannot be withdrawn through another.
Before you choose one anchored BTC token over another, make sure you trust the issuing anchor, and that you understand the conditions for that token’s redemption.