The document provides information about biological databases and sequence identifiers. It discusses the main objectives of biological databases which include information systems, query systems, storage systems and data. It describes primary databases like GenBank, EMBL, DDBJ, UniProt and PDB as well as secondary curated databases like RefSeq, Taxon and OMIM. It also explains different types of sequence identifiers used in databases like LOCUS, ACCESSION, VERSION, gi numbers and protein identifiers.