DHT, Distributed Hash Table, a way to store pairs in distributed manner. Each data element (value) is identified, addressed and accessed by its key in an efficient manner. Usually a hash function is used to hash the key to the address base of the DHT and corresponding value is stored under this address.
GUID, Globally Unique IDentifier, a name for the resource that makes it unique in the global name space. Assigning a GUID enables each to be unique so that users cannot overwrite the resources of the others that are in the same namespace.
File Catalog, is used to store the mappings between one logical file name and many physical file names. Then user or middleware can choose which physical copy to access when a file is queried by using its logical filename.
Replica is an identical copy made of a file or a collection of files. Replicas are usually created to make file access faster and make data available closer to the site where it is used.
LFN, Logical File Name is the user-defined name for accessing the file in the system. The LFN is used to access the file from the user interface. The grid middleware maps the LFN to physical location of the file to access the file from it’s actual location.
PFN, Physical File Name is the actual location of the file or a replica of the file. System can access the file using this URL as a contact string to the file.