A cash-secured put is a short put with the full cash reserved to buy 100 shares per contract at the strike if assigned. The premium is kept either way; assignment converts the reserve into stock at the chosen strike.
The cash reservation is what separates the structure from naked put selling: assignment is a planned acquisition rather than a margin event. The entry criterion that premium never overrides is willingness to own the stock at the strike. CSPs commonly target around 0.25 delta in a 30-45 DTE window and form the first state of the wheel.