Hahn  is in Rhineland-Palatinate, Germany, about 100 km west of Frankfurt. The town of Hahn is somewhat overshadowed by its airport, Frankfurt-Hahn, used by many budget flights as an entry point to Frankfurt.
Hahn (IATA: HHN)  airfield is a major destination for various budget airlines, mostly notably Ryanair. Recently, the airport calls itself "Frankfurt-Hahn", even though it is located about 100km away from Frankfurt (travel time is about 90 min by bus).
The place is vigorously being developed and the airport has a nice, modern terminal, full of shops and bars. There are a couple of hotels nearby and more being built. Several major car rental companies have outlets here.
The main contributor to such a change is an Irish budget airline Ryanair, which made Hahn one of its European bases and offers flights to numerous European destinations such as Bologna in Italy and Riga in Latvia. Ryanair has suffered some ridicule because the airport's name includes Frankfurt. However, the airport provides good access to the towns along the Rhine and Mosel rivers and to the countryside of the Husruck, an area featured in the epic series Heimat.
A number of bus companies operate direct services to Hahn from cities in the region, including Frankfurt, Trier, Luxembourg, Metz, etc. The operators, routes and timings change constantly so see the official site for up-to-date listings.
Be aware that the bus from Frankfurt Airport can be full (as it goes from the centre of Frankfurt and makes a stop at Frankfurt Airport Terminal 1), especially when time is close to popular Ryanair flights to Italy. If you have big bags, be aware that the baggage compartment of a bus can be full, too. Allow plenty of time if having to go from Frankfurt airport to Hahn airport for a connecting flight. The main airport FFM and Frankfurt - Hahn are 2 hours apart.
Hahn is located along the B-327, a short distance from the B-50/E-42 between Bernkastel-Kues and Kirchberg.