Test Driven Development Practical Solution(Industry Expereince) in existing projects and new projects

I am a bit confused with TDD concept and it's practical application in organizations, I am highlighting the word practical so please don't give me theoretical answers.(like write test first,fail it, just pass it, add new functionality, then refactor code, repeat cycle). This will be annoying.

I am asking from practical application in Software industry.Guys who are doing software development in IT industry, please share your experience on TDD and how you implemented it practically in existing project and also in new projects.

These days company stresses much on TDD required for a developer role, but I don't think practically the theoretical definition of TDD is followed. Mostly what I think on TDD is every class we write should be able to be unit tested in isolation.Necessarily it means each application class has a unit test class.

Please share your practical industry thoughts and how you applied TDD in software projects.