The difference between Bithumb.com and Bithumb.pro is that the pro variant focuses on clients outside South Korea, hence the reason it refers to itself as Bithumb Global.

https://coinmarketcap.com/exchanges/bithumb/ Native KRW trading pairs.
https://coinmarketcap.com/exchanges/bithumb-global/ Native USDT and BTC trading pairs.

To some degree it's a similar construction as Binance.com and soon Binance through BAM trading services that plans to serve users that the Binance.com site not accepts through a proxy.