The largest crypto exchange by volume
An overseas exchange cannot accept KRW directly. The usual route is to buy on a domestic exchange and transfer the coin, and choosing the wrong network (chain) at that step can lose the funds permanently. Always test the first transfer with a small amount and double-check both the address and the network.
Income earned on an overseas exchange is still taxable, and holdings above certain thresholds can trigger foreign account reporting duties. Sorting out the tax side before you start trading is far easier than doing it afterwards.
Signing up through a referral link can apply benefits such as a trading-fee discount. The exact benefit and its conditions change with exchange policy, so check what is shown on the sign-up screen itself.
The biggest difference is KRW in and out. A domestic exchange takes won directly through a verified bank account, while an overseas one needs you to transfer crypto in. In exchange, the range of listed assets and derivatives is usually wider.
Fees depend on your volume, token holdings and the product, and the policy changes often. Rather than memorising a number, get into the habit of checking the official fee page before you trade.