This is a port town, particularly for the fishing industry and is the nearest town of any size to Bromo-Tengger-Semeru National Park. The latter is main reason any vistor comes here as there is little else of interest. The park is sometimes day tripped from an accommodation base at Probolinggo.
Be sure to go all the way to the main bus terminal, 6 km southwest of the centre, instead of getting dropped off at some travel agent (who will pay the driver a commission). Minibuses to Cemoro Lawang, the nearest settlement to Bromo-Tengger-Semeru_National_Park leave from the terminal and take about an hour and a half. Purchase any tickets directly at the bus terminal, as the local travel agents are notoriously mercenary and will happily charge you multiples of the real price and/or fake return tickets.
For most people Probolinggo will only be a transfer point to get to Mount Bromo. If arriving by train (from Banyuwangi or Surabaya), you will already be spotted on the platform and freighted in an angkot to the bus stand to Cemoro Lawang (INR 3 000). There travel agents will try to sell accomodation and tours, but they aren't too persistent. Just pay for the transport (mini bus, INR 25 000, 2 hours) and you should be on track soon. When arriving by bus, the procedure should be similar.
Probolinggo is famous for its small, sweet green mangoes, known as manalagi mangga.