The word konbanwa is a Japanese phrase that means "Good Evening".
Konbanwa in Japanese is a way of greeting someone meeting then in the evening or late afternoon.
The Japanese phrase konbanwa is also similar to saying "hello" to someone after dark in English.
But not as a farewell like "good night".
When you say konbanwa to someone in Japan you're telling them, "Good Evening" or "Hello in the evening".
The usage of konbanwa in Japan is a greeting for the evening hours, and used when arriving or meeting someone.
The distinction of konbanwa is that "konbanwa", is a greeting, and not a goodbye.
For saying farewells in Japanese you would use phrases like, "Sayonara" which means goodbye and "Mata ne" for see you later.
The Japanese phrase, "konbanwa" can be used in both formal as well as informal situations in Japanese.