However, it's usually used as an informal expression in Portuguese, similar to the English "good one!" or "nice!" It's a way of saying "that's good" or "that's nice" in response to something someone has done or said.
Here are some examples:
* "Você fez um ótimo trabalho!" - "E uma boa!" ("You did a great job!" - "Good one!")
* "Eu ganhei na loteria!" - "E uma boa!" ("I won the lottery!" - "Nice!")
So, while it translates literally as "and it's good," it's best understood as a more informal expression of agreement or appreciation.