Caulking/sealant is a bead of (silicon, latex/acrylic, polyurethane, butyl/rubber) specific material that seals the penetrations, gaps, cracks and material intersections.
In actual caulk and sealant are two different names used interchangeably, but there is a difference in elasticity. Sealants (for example, silicon) are more elastic than caulks (latex/acrylic). For the sake of simplicity, we are using the word caulking here for both caulk and sealant.