In addition to Rishabh Shandilya’s answer,

Xpath:- 
XPath is one of the Mendix query languages designed to retrieve data. XPath uses path expressions to select data of Mendix objects and their attributes or associations.
 

Examples of XPath queries are:

• //Sales.Customer Retrieve all customers.
• //Sales.Customer[Name='Jansen'] Retrieve all customers with name ‘Jansen’.
• avg(//Sales.Order[IsPaid = true()]/TotalPrice) Retrieve the average of the total prices of all paid orders

 For more details about xpath you can refer this youtube video here :-
https://www.youtube.com/watch?v=sdabUY-w4ZU&t=3s

Microflows:-
Microflows allow you to express the logic of your application. A microflow can perform actions such as creating and updating objects, showing pages and making choices. It is a visual way of expressing what traditionally ends up in textual program code.

Microflows run in the runtime server and can therefore not be used in offline apps. For application logic within offline apps, see Nanoflows.

This page is a summary of the elements which make up a microflow, together with their visual representation within the microflow. It also covers keyboard support when editing microflows.

For the properties of the microflow itself, see Microflow Properties. For more best practice details, see Microflow Naming Conventions, Microflow General Best Practices, and Microflow Best Practices from the Community

For more details about Microflow’s you can refer this mendix doc below :
https://docs.mendix.com/refguide/microflows/

Hey Karthik,

You can refer to these docs, they can give you a pretty good idea about what Xpaths are and how we use them,

https://docs.mendix.com/refguide/xpath-source/

and 

https://docs.mendix.com/refguide8/xpath/

Hope it helps!