What do you mean by predictable 3000 IOPS baseline performance (gp3)

From the AWS documentation:
General Purpose SSD (gp3) volumes offer cost-effective storage that is ideal for a broad range of workloads. These volumes deliver a consistent baseline rate of 3,000 IOPS and 125 MiB/s, included with the price of storage.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-volume-types.html