BDD or Behavior Driven Development and TDD or Test-Driven Development is the two approaches to Software Development. BDD focuses on the end-user application. Whereas, TDD dwells more on the functionality aspects. BDD test scripts are written in Gherkin, which facilitates more non-technical members collaborating as it is written in English and makes way for better readability as opposed to programming scripts in TDD, which are written in Java, Ruby, etc.
If you wish to break into the automated testing arena, I would suggest you check out the Selenium certification course from Intellipaat you as it offers you dedicated training and project work to help you build your practical skillsets. Also, have a look into the Selenium tutorial and video on Selenium Tutorial for Beginners.