Django (/ˈdʒæŋɡoʊ/ jang-goh) is a free and open source web application framework, written in Python. A web framework is a set of components that helps you to develop websites faster and easier.
When you're building a website, you always need a similar set of components: a way to handle user authentication (signing up, signing in, signing out), a management panel for your website, forms, a way to upload files, etc.
Luckily for you, other people long ago noticed that web developers face similar problems when building a new site, so they teamed up and created frameworks (Django being one of them) that give you ready-made components to use.
Frameworks exist to save you from having to reinvent the wheel and to help alleviate some of the overhead when you’re building a new site.