What is xbtc? I saw many articles refered xbtc,just like "btc to xbtc". But there's no material telling what it exactly is.
XBTC is an asset representation of BTC in Counterparty.
Apparently, you could send Bitcoin to a Counterparty gateway, and get the same amount of XBTC back in turn. These could then be traded for other Counterparty assets. The operator of that gateway claimed that it was cheaper to trade thusly than on Bitcoin exchanges.
XBTC is the combination of ISO 4217 currency code XBT and the name BTC, which is also commonly used to represent one bitcoin, but it violates ISO 4217 because it begins with "BT", the country code of Bhutan.
This is what is known as a blended word, which Lewis Carroll called portmanteaus, naming them after a suitcase that unfolds into two equal parts.