A is a Jones Fracture, a fracture at teh metaphyseal-diaphyseal junction of the 5th metatarsal.  These are clinically significant because due to poor vascular supply (vascular watershed area), they are at greater risk of nonunion (30-50%).  These fractures are treated as non-weight bearing, with a short leg cast for 6-8 weeks, in some cases they require surgical intervention

B is a pseudo-Jones Fracture, which involves the proximal tubercle of the 5th metatarsal (and rarely enters the 5th tarsometatarsal joint).  Interestingly, these often look worse on Xray than Jones fractures, however, they are not prone to nonunion and usually are treated with a hard soled shoe, boot or cast with protected weight bearing.  These patients may return to normal activity early, however, they  may still have pain for up to 6 months.