A withdrawal is the reverse of a deposit, and it has its own set of failure modes, because the money is leaving a place you do not control. This is how it works, what it costs, and the mistakes that are expensive to fix.
The mechanics
You open the withdrawal screen, choose the coin, enter the destination address, and confirm. The market processes the request, deducts the 1 percent fee, and sends the coins to the address you gave. In normal conditions the send happens within the hour. The minimum withdrawal is small, so there is no threshold that traps a balance, and there is no schedule that holds withdrawals on a fixed cycle.
The fee is flat, 1 percent of the amount, applied before the send. A withdrawal of 1 XMR comes out as 0.99 XMR. It is not a lot, and it is the market's revenue line, so it is not going away.
The three mistakes
The first is the wrong address. A withdrawal to a mistyped address is a transfer to a stranger, and there is no recall. The fix is the same as for everything else on the dark web: copy the address, do not type it, and check it twice before you confirm.
The second is the wrong coin. Sending Monero to a Bitcoin address, or Bitcoin to a Monero address, does not arrive. The coin you withdraw must match the network of the destination address. The market warns you about a mismatch, but the warning is easy to dismiss, and the coins are not easy to get back.
The third is the withdrawal while a dispute is open. If a portion of your balance is tied to an open dispute, that portion is not available for withdrawal, and trying to move it produces an error that looks like a system problem but is just the escrow doing its job. Close the dispute first, or withdraw the rest and leave the disputed amount where it is.
Timing and congestion
The market sends when it sends, but the coin's network decides when the transfer confirms. A congested Bitcoin network can add an hour or more to the confirmation, and the market does not control that. If a withdrawal has not arrived after a day, the first check is the coin's block explorer, using the transaction ID the market gives you. If the transaction is on the chain, it is on its way, and the wait is the network's, not the market's.
The fees guide covers the cost structure in full, and the escrow guide explains why the disputed portion is locked.