It may seem like all jackets are the same, but there are big differences between a blazer, a suit jacket, and a sport jacket.
A sport jacket has nothing to do with tracksuits or t-shirts. The term sport jacket came about because gentlemen used to do sports like horse riding and hunting while wearing them. A sport coat is less formal that a suit coat.
Sport coats are usually made of wool, tweed, or more exotic fabrics like corduroy, cashmere, or velvet. It usually has two to three buttons and can have a texture or pattern.
The cut is similar to a suit jacket. An American style jacket is has one cut in the back while a British style jacket has two cuts and a continental style jacket does not have a cut.
A sport jacket that is matched with nice pants and a shirt is a good for business casual events. For more informal occasions, a solid navy jacket can be paired with jeans or chinos and a colorful shirt. Sports jackets are not appropriate for formal meetings and parties.