Memory cards are used to store game saves, additional levels, character profiles, and other data on the PlayStation 1. Without a memory card, players cannot save their progress in games, unlock new levels, or customize their gaming experience.
Some PlayStation 1 games require a memory card in order to function properly, while others may simply disable certain features. The game manual will usually specify if a memory card is required or recommended.
If a player does not have a memory card, they can still enjoy some PlayStation 1 games by playing them in the guest mode. Guest mode is a temporary profile that does not allow for saving game progress, but it does allow players to experience the game's content.
Overall, while it is possible to use a PlayStation 1 without a memory card, the experience will be limited and many features will be unavailable.