What are the differences between, and the connotations of, "flag", "banner", and "standard"?

Flags and standards derive from the need to identify which side of the battle one was with during military conflict and many carry the coat of arms of the person under whose name one was fighting. Flags were also used for communication before electronic means could be used; and they are used to identify individual countries, of course.

Standards, however, are a type of flag used for personal identification and will only carry the coat of arms of its owner, such as the Royal Standard in the UK or the personal standard of any armiger. Hence, a standard is a type of flag but a flag isn't necessarily a standard. They are not necessarily triangular in shape nor hung with bunting on a ship.

A banner is a long strip of fabric or plastic bearing a slogan or design, carried in a demonstration or procession or hung in a public place. Bunting was the name of the fabric from which triangular-shaped flags were made which when sewn together can make a festive sight on a ship. Nowadays 'bunting' is used to describe the flags as well as the tape that keeps them together. Using communication flags, bunting can be used to carry messages, such as "England expects that every man will do his duty."