Chain Split Tokens (CSTs) are an innovative new token class created by Bitfinex to allow market participants to speculate on the future outcome of a potential cryptocurrency protocol change.
The first such tokens were for a potential Bitcoin Unlimited hard fork.
Please consult the original announcement post for these CSTs - the BCC and BCU tokens. Then, thoroughly review the terms and conditions for these CSTs.
Finally, you can access the trading of these pairs and the Token Manager from the main website's "CSTs" dropdown menu.