A FASTA file is a plain text format used to store nucleotide or protein sequences. Each entry in a FASTA file begins with a header line, starting with a ">" symbol, followed by a description or identifier of the sequence. The sequence itself is written on subsequent lines using the standard nucleotide or amino acid codes (e.g., A, T, C, G for DNA sequences). It is a widely used format for storing reference genomes, genes, or any other sequence data. FASTA files are compatible with most bioinformatics tools and are essential for tasks such as sequence alignment, motif discovery, and gene annotation.