Biological databases are essential for storing, organizing, and analyzing biological data, which can include sequences, structures, interactions, and functional annotations. These databases can be classified into three broad categories: primary, secondary, and composite databases, based on the type of data they contain and their purpose in bioinformatics. Primary databases store raw experimental data directly obtained from research studies. These databases often contain unprocessed data, such as genetic sequences or protein structures, which are curated directly from the experimental results. Examples of primary databases include GenBank, which is a comprehensive repository of nucleotide sequences; Protein Data Bank (PDB), which stores three-dimensional structures of proteins and nucleic acids; and the EMBL Nucleotide Sequence Database, which is similar to GenBank and provides access to sequence data. These databases are critical for sharing raw data, which researchers can use for further analysis and interpretation. Secondary databases, on the other hand, are derived from primary databases but include processed or curated information that has been analyzed, annotated, and organized to provide additional context. These databases typically contain