A blazer is a wildcard, it can be worn both in casual contexts and in casual business meetings. It's less formal than a classical suit jacket, and the perfect companion for your weekend activities, because it has a casual elegance that's inappropriate on formal business occasions.
The blazer is traditionally a thigh-length, double-breasted jacket, tailored in either black or navy lightweight flannel. The brass buttons on the sleeves reflect the garment's origins in late 19th-century British boating and cricketing culture.