DBFS is the "Databricks File System", but really it's just a shim / wrapper on top of distributed storage, that makes files in S3 or ADLS look like local files under the path /dbfs/... This can be really useful when working with libraries that do not understand distributed storage. They can read/write distributed storage as if it's a local file. DBFS also lets you mount other buckets under different paths under /dbfs. That's about all it is though, just a translation layer that exposes distributed storage under /dbfs (or under dbfs:/ URIs)