In this Flask video lesson we want to learn How to Use Flask SQLAlchemy, so Flask SQLAlchemy is an extension for Flask that provides simple way to integrate SQLAlchemy, it is powerful Object Relational Mapping (ORM) library into Flask applications. SQLAlchemy is  popular Python library that allows developers to interact with relational databases using Python code, and this makes it easier to work with databases without having to write SQL code.

SQLAlchemy provides different features that simplify the process of working with databases including:

1. Object-relational mapping: SQLAlchemy allows developers to define database tables as Python classes, and this makes it easier to work with database objects using object oriented programming techniques.
2. Database migration support: SQLAlchemy provides builtin support for database migrations, which allows developers to easily modify the structure of their database schema over time without having to manually modify the database.
3. Query generation: SQLAlchemy provides powerful query generation system that allows developers to generate complex database queries using Python code instead of raw SQL.
4. Integration with Flask-Script: Flask SQLAlchemy integrates seamlessly with Flask-Script, a command-line interface extension for Flask, and this makes it easy to create command-line tools for managing databases.