I did not undersantd why in the middle of Romania, Hungarian is spoken. The best way to find out is by asking to the people who live here but, they compare it with Catalonia (an autonomous region in Spain). After a long conversations with the locals, now I know.

It all began after the First World War, in 1920 with the Trianon treaty. Hungary gave part of its territory to Rumania (Transylvania and other territories), Yugoslavia (Slovenia, Croatia). Italy, Austria and Poland also got a little part of Hungary´s territory. Although Hitler gave back its territory to Hungary, when the Second World War finished, Hungary lost its territory again. 

Târgu Secuiesc (in Rumanian) or Kézdivásárhely (in Hungarian) is part of the territory of Székely. It is in county Harghita, Covasna and Mures. Székely country had considerable but changing autonomy due to its military role. They are still in search of their autonomy, like Catalonia. 

However, governments are reluctant to give independence to the richest regions in their respective countries.