Every object has an unique ’official’ name which is made of a database code followed by a colon followed by an identifier. For example, sw:HBB_PHORU is the Swiss-Prot entry that describes the hemoglobin beta chain (HBB) of the greater flamingo (Phoenicopterus ruber).
Synonyms are "alternative names" to designate an entry. As an example, you can retrieve an entry by its accession number(s), or its CRC64 checksum. A warning message is always issued when a ’synonym’ is used to retrieve an entry.
What can you tell of the following names: HBB_PHORU, P02121, 625378EECD884A27 and of this one: 430750B39969978B?