The MEMO / TAG is required because for some coins-tokens it is not enough to just enter your crypto address, you will also need to fill an additional "message" field. In this field, it is necessary to enter the MEMO / TAG that your wallet provides.
For example, in the case of Ripple, you need to enter TAG, which is a sequence of 9 digits. In the case of BNB, XLM, and HBAR, a MEMO is required. For BNB you need to enter it because all Binance users have the same BNB address, and only the MEMO is unique.
If you leave the MEMO / TAG section blank when placing an order, our system will perceive it as if your wallet doesn't need this extra information. But in case your wallet did need this information, your order either will be sent to the central address of the exchange or can be lost forever.
Please be careful and take extra care to provide all the necessary details before finalizing your order!