
What Flask Do?
Web Framework
The Web Framework, is a collection of tools and modules that allow a web application developer to construct apps without worrying about low-level issues like protocols, thread management, and so on.
WSGI
The Web Server Gateway Interface (WSGI) has been approved as a Python web application development standard. WSGI is a standard for creating a uniform interface between a web server and a web application.
Werkzeug
It is a WSGI toolkit, which implements requests, response objects, and other utility functions. This enables building a web framework on top of it. The Flask framework uses Werkzeug as one of its bases.
Jinja2
jinja2 is a popular templating engine for Python. A web templating system combines a template with a certain data source to render dynamic web pages.

