Hailing from the USA, bomber jackets were originally used by pilots to stay warm in difficult flying conditions. Generous ribbing around the cuffs and waist allowed for good insulation against the cold and the traditional, bright orange lining meant that the pilot could turn their jacket inside out to more easily attract the attention of rescuers in the event of a crash.
US-based Alpha Industries still produce the original bomber jacket, but nowadays, most jacket makers have launched their own interpretations of the bomber in a wide range of colours and materials. Bomber jackets work particularly well together with jeans or chinos in shades of grey, blue, brown and green. The short cut of the jacket makes for a very casual look.
Try experimenting by combining it with a white shirt, together with a tie in the same colour as the jacket or with a crew neck t-shirt underneath.