GRANT ALL PRIVILEGES----- Means you are granting Insert, delete, alter and all DML permissions.
ON cwkdb.* ----If you want to grant permission to do some operations then you need to tell on whom you are going to perform the operations, I mean Table or functionetc. here it would be cwkdb.
TO cwk@localhost---- You need to identify the person or user to whom you are giving these permissions---- user specification