Pending Period
The pending period is the gap between when you click "withdraw" and when the casino actually processes your payment. During this time, your money sits in limbo. The casino hasn't sent it yet, and depending on the casino's policy, you might still be able to cancel the withdrawal and put the money back into your account (which is a dangerous feature by design).
Pending periods vary wildly. The best casinos process withdrawals instantly or within a few hours. Average casinos take 24 to 48 hours. The worst ones stretch it to 72 hours or longer, and some add "business days only" which means a Friday withdrawal might not process until Tuesday.
A long pending period is a red flag but not always a deal-breaker. Some otherwise-reputable casinos have 24-48 hour pending times simply because their compliance team manually reviews each withdrawal. What you want to avoid are casinos that combine long pending periods with a reverse withdrawal option, because that combination is designed to tempt you into giving the money back and continuing to play.