What does WB stand for?

Write Back

Write back is a storage method in which data is written into the cache every time a change occurs, but is written into the corresponding location in main memory only at specified intervals or under certain conditions. When a data location is updated in write back mode, the data in cache is called fresh, and the corresponding data in main memory, which no longer matches the data in cache, is called stale. If a request for stale data in main memory arrives from another application program, the cache controller updates the data in main memory before the application accesses it.