On some networks, for example Stellar, many accounts share one deposit address. The memo (also called tag or comment) tells us which account the deposit belongs to.

Deposits

For such networks the Receive page shows a Memo (tag) under the address, with its own copy button and QR code. When you send, enter both the address and the memo. Copy the memo exactly.
A deposit without the memo or with a wrong memo is not credited automatically, but it can usually be recovered on request: send a recovery request through the support form with the transaction ID. Each case is checked manually, a recovery fee is deducted from the recovered amount, and there is no guaranteed time: Can a deposit that was not credited be recovered?
If you send from another exchange, make sure it lets you enter a memo for this network.

Withdrawals

Many exchanges also require a memo or tag for deposits on such networks. Take it from the deposit page of the receiving platform.
For networks that support a memo, the withdrawal form shows a Memo (tag) field. Enter the memo there only if the receiving platform requires it; otherwise leave it empty.
If you see This memo cannot be sent in this network, the memo has a format the network does not allow: check it with the receiving platform.
Sending to another Strade user on such a network: enter the Strade address and the receiver's memo. Without a memo you see This is a Strade deposit address. Enter the recipient's memo (tag)., with a memo no Strade account has No Strade account has this memo; nothing is sent. See Sending to another Strade user.
If the receiving platform requires a memo but the withdrawal form has no Memo (tag) field for this network, our withdrawals in this network cannot carry a memo: do not send. Choose another network the receiver supports, or write to the support form.

Stay safe: Strade support never asks for your password, 2FA codes or seed phrase.

What is a memo (tag) and when do I need it?