Script Task Vs User Input Task

Did you attend the Appian academy? I think this is covered.

https://docs.appian.com/suite/help/21.2/Configuring_the_Script_Task.html

docs.appian.com/.../Configuring_the_User_Input_Task.html

1.  User input task node allows a designer to associate an interface to an user attended activity.
For detailed information about how to design interfaces, including how to enable user interactions, how to save and validate user inputs, and how to submit user inputs to process, see the Interface Object page. 

2.  The Script Task is used to perform an automated activity (which does not require a user to complete a form). It is typically used to execute an expression or rule and capture it in the process variable and use it further in a process. 

Agreed, I'd also highly recommend the Academy Online training courses. These courses provide answers to all the questions you have asked: community.appian.com/.../courses

Conceptually ALL steps/nodes/smart services in a Process Model are "tasks". But it's only a "User Input Task" that is used to present a form/user interface to a User for, you've guessed it, "input" from that User! All other "tasks" have either very concrete functionality (e.g. "Write to Datastore") or the more abstract "Script Task" (which can invoke a wide range of  functionality in the rule!, fn! or a! domains)

Sir why do we configure only node outputs on script task ?

If i configure node inputs of a script task is it a mistake ?

No, because you have the option to derive a value for your "input" in the 'Value' property and then write that value to a process variable in the 'Save into' property:

What is the difference in node inputs and outputs ? I am unable to figure out

As per the documentation generally only node outputs are configured for script task and not node input ?

Basically the node input name is a activity class parameter confined to a node and the node output will provide us to map dynamic expression onto process variables ?