I feel like this is the default work-related greeting. Most literally, it means something like "thank you for the hard work," but it really depends on the context. If you say it at the end of the week over beers, it means "we made it to the weekend." If you say it at the end of a project, it means "good job." It can also be said in the morning to mean "hello," or at the end of the day to mean "see you tomorrow."