You can consider frameworks as a skeleton of your automation project. Whenever you try to automate a system, you would not want to create an automation script that would not be reusable. You might intend to create an Automation script that would cater your need to automate the system with an additional intent to reduce the time taken to traverse your system and male savings and reduce manual intervention.
A framework provides you with a feature of progressively reading the data kept somewhere and using it in your application to create a script. Now, this data can change every time you access your application.
Frameworks also allow you to read the data from an external data source like excel sheet or database and input the data in your web or desktop application thereby making your Automation script reusable.
There are three kinds of frameworks commonly used in Selenium which are as follows:-
1. Keyword-driven framework
2. Data-driven framework
3. Hybrid (Combination of both Keyword and Data) framework
If you are planning to learn Selenium then I will suggest you must take up the following Selenium Training Course. You can also watch the following video tutorial to know more about frameworks in Selenium..