BLASTX is generally used to find protein coding genes in genomic DNA or to identify proteins encoded by transcripts.
Most proteins are related to other proteins. This makes BLASTX a very powerful gene-finding tool. As protein databases become larger and more diverse, BLASTX becomes even more useful because it can identify more and more genes.
Net-BlastX is a variant of the BlastX program intended for work with distant databases.
BLAST is a service of the National Center for Biotechnology Information (NCBI). A nucleotide or protein sequence sent to the BLAST server is compared against databases at the NCBI and a summary of matches is returned to the user.
The www BLAST server can be accessed through the home page of the NCBI at www.ncbi.nlm.nih.gov. Stand-alone BLAST binaries can be obtained from the NCBI FTP site.