This is used at the beginning of a phrase or an idea as a way to describe something you did intentionally that goes against what you would normally expect. For example, Pharrell あえて wore shorts with his tuxedo as a way to defy the expectations of formal red carpet wear.
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."
You use it as an exclamation or a compliment towards someone when they meet or exceed your expectations when doing something. It's usually a compliment of saying "of course you can do it" with the subtext being, "because I know you're so capable."
意識が高い (ishiki ga takai)
It translates to high consciousness or awareness, and it refers to someone who's aware of global & social issues or is generally knowledgeable. However, it carries a slightly negative connotation of being slightly snobby or know-it-all and it isn't necessarily a good thing.