The two names point to the same immigrant visa for a spouse; the only thing that separates them is how long you've been married when your spouse is actually admitted to the United States.
If the marriage is less than two years old on the day your spouse is admitted, they receive a two-year conditional green card — that's the CR-1, where "CR" stands for conditional resident. Before that card expires, the two of you file Form I-751 together to remove the conditions and convert it to the standard ten-year card.
If the marriage is two years or older at admission, your spouse skips the conditional stage and receives a full ten-year green card straight away — that's the IR-1, for immediate relative. Same petition, same process; the marriage's age at the moment of entry decides which card prints.
Information current as of July 2026. If your spouse arrives on a CR-1, the I-751 step comes later — read about removing the conditions on a green card →