The phrase "separate cribs" means that there are two or more cribs for babies that are not connected or placed together. Each baby has their own crib. Full definition
My twin boys share a room but sleep in separate cribs, which seems like a good compromise. (get-your-baby-to-sleep.com)
Once they get old enough that they start moving and rolling around, it's definitely time to have them in separate cribs, though. (momtricks.com)
There isn't enough evidence at this time to say that sleeping together is safe, so they instead recommend separate cribs or playpens. (verywellfamily.com)