I recently started working in a place in Berlin, Germany, and though my German is OK I guess, there's a common term that I don't understand. It's Mahlzeit.
When people leave from work around lunch time, they say that and people around respond with the same. According to dict.cc it means "Enjoy your meal!".
Is this a common German term or is it just a thing in Berlin? What does it mean exactly? And do you have to respond with Mahlzeit or are there other responses one may use?