Maybe it's a good idea to take a step back and define URL before going deeper into https and its usage. URL stands for Uniform Resource Locator commonly known as a web address. A good way to think about what it does is to imagine it as an address that does two things. Firstly, it tells you where something is and secondly, how to get it. Usually what you are looking for is a webpage found on a computer somewhere on the internet (web server). The URL is made up of several parts but in this article we will focus on one - the protocol namely https and http.
The protocol in this context is just a set of rules computers must follow in order to communicate effectively with each other. HTTPS stands for Hyper transfer protocol secure and HHTP stands for Hyper transfer protocol. I know what you are thinking, what's the difference. Well, https is just http but with encryption meaning it's more secure.
So in short, websites use https as it allows data to be exchanged between a users computer and a site in a way that protects the integrity and confidentiality of the data being exchanged.
Some general tips regarding https
Verify status and error codes - Ensure that your website returns the correct applicable codes e.g. 404 for pages that do not exist
Matching content - if you have http and https sites, ensure that the content is the same
Security elements - Only embed https content on https pages
Upgrade the to the latest secure protocol if you haven't already
Don't block your https site from being crawled unless necessary