Hi.  
Beta means the same here as it means in other areas of development.  
You can trade on it right now.  
In fact ANY pair from this list:

Bitcoin (BTC) | Blocknet (BLOCK) | Dash (DASH) | DigiByte (DGB) | Dogecoin (DOGE) | Dynamic (DYN) | Faircoin (FAIR) | LBRY Credits (LBC) | Litecoin (LTC) | Monacoin (MONA) | MonetaryUnit (MUE) | Namecoin (NMC) | PIVX (PIVX) | Qtum (QTUM) | SysCoin (SYS) | Vertcoin (VTC) | Viacoin (VIA) | XCurrency (XC)

The reason it is a beta is because over the next few months, there will be more automation, setup will become easier,  feedback and ideas from users and the community will be integrated as well as bug fixes until we reach SPV wallets in July at which point it will be considered a full release.  Between now and then, the marketing will also slowly ramp up.