Retro is a term often used in Eastern and Central Europe for things that are left behind from the end of the 20th century, or, in an increasing number of cases, have been recreated to resemble the typical looks of those things. Unlike 'old', retro doesn't imply that the thing is incapable of doing its job anymore, just identifies it as something which has a unique style to it because of the year it was made.
When talking about trains, we must differentiate between retro vehicles and historic vehicles, both can mean locomotives, carriages or multiple units and railcars. Something is historic if it is kept in a museum or is only used on special occasions. They are often privately owned or belong to an identity separate from the railway companies that serve the usual traffic in the region. Retro, on the other hand, usually means a vehicle that still has some daily work to do and is actively used to earn revenue in ways which are not connected to the tool being older than the average stock. To put it straight: they carry passengers just like any other vehicle belonging to their operator or are used for daily freight or departmental trains. But they all wear a special livery that can turn back the wheel of time for the people who remember, force some good memories to resurface and add a significant bit to the class and mood of rail travel. In the UK this kind of repainting is often called a heritage livery.
The Hungarian network is not the only one to have retro trains, but the number of such vehicles has greatly increased recently and for the second year in a row, passenger operator MÁV-START has organized special Retro Weekends for enthusiasts and the general public to enjoy, thus bringing attention to the existence of these nice vehicles.
Bzmot 343 (117 343 in the current numbering scheme) is allocated to the MÁV-START depot at Balassagyarmat and wears the livery these tiny railcars had worn until the mid-90s refurbishment and engine replacement.