FASTA help page

FASTA formatting is a simple, standardized method for formating DNA and amino acid sequences and storing the in text files. For each sequence in a file, FASTA formatting consists of a greater than sign ('>') followed by a title for the sequence, then a newline character. The the sequence begins on the next line. Here's an example sequence of a human heavy chain V gene segment:

Sequences obtained from databases like IMGT, NCBI, Genbank, and other databases can be automically fortmatted into FASTA format during the download. See those tools' help pages for instructions on doing so.