Google Web app is like a Web page/web application that can be used for multiple purposes, such as collaboration for small teams and restricting external teams from directly accessing the data in google sheets but only through UI. You can use google sheets like a database storage and build a user interface on top of it to control how users interact with the data.
 
What you will get with the purchase:
 
A zipped file includes a step-by-step guide and a file that includes the script.
 
Note: you should have some basic knowledge of google sheet/excel.