Very often on some exchange (Binance above all), in addition to the wallet address (where to send a crypto), "𝕥𝕒𝕘" or "🅼🅴🅼🅾" are requested. These are combinations of letters and numbers.
What are they for? They are used to identify the transaction and to properly deposit funds.
Some centralized exchanges use the same address for multiple users. This is especially true for XRP and XLM that require a deposit for address activation. Why? Because it is economically advantageous to have only one address for many users.
CENTRALIZED EXCHANGE: TAG / MEMO
The memo ID and tags are used to determine which account a particular transaction should be credited to. If you use the Binance Chain and don't specify the tag, you risk losing your funds.
To do this we note that when you try to send some crypto (XRP, BNB, XLM, EOS, XMR, etc) in addition to the address we will also have to insert a tag / memo. Going to the address of your wallet we will notice that there is also a tag (so to receive those tokens at that address I will also have to provide the tag).
DECENTRALIZED WALLETS: NO TAG / MEMO
IF YOU HAVE TO RECEIVE on Atomic you don't need a destination tag, memo ID, message or payment ID because this wallet creates a unique address for each user. If you have to enter something, you can enter random numbers.
IF YOU SEND from Atomic Wallet to a centralized Exchange (such as Binance), you must specify a destination tag or memo.
Even Trust Wallet, upon receipt, does not require tags or memos.
If I send from Binance to Trust (or Atomic) I can insert a random memo. If I do the reverse step and use some tokens that need memo tags I have to insert it (otherwise not only the transaction will not be processed but I will lose my funds).