BDD is extension of TDD(test driven development)
-In BDD we are writing SCENARIOS from
End Users perspective.

BDD has 2 sides:
1- Business side: Feature files where we use 
Gherkin language to write our scenarios.
Gherkin is very similar to English. That's why
it makes everyone in the team on the same page

Also there is 
2-Implementation Side: Where we actually implement
the programming logic that automates the application.