Google Cloud's object storage service. It stores objects in buckets with 11 nines of durability. Storage classes: Standard, Nearline, Coldline, and Archive, based on access frequency.
In CDL it's the equivalent of S3 (AWS) and Azure Blob Storage. Question: object storage on GCP → Cloud Storage. For files accessed monthly → Nearline. For files accessed yearly → Coldline or Archive.
Cloud Storage (GCP) is a concept that can show up on the exam. Check the full guide to see it in context.