Back End developer are responsible for the code that interacts with the web server and performs special functions. They use languages and technologies such as PHP, Java, and NodeJS.
Databases are huge collections of information. Database developers are responsible for writing the code that gets and saves all the data from a website. They use languages and technologies such as SQL and Mongo.
Public facing websites, the websites you and I visit every day, are extraordinarily important for both businesses and customers. With the ever growing number of smart phones and computers in the world, everyone turns to the web for information. So how do companies get that information to the customer? A website. That's how. And Web Developers help make that happen.
Many large companies utilize what is called "Software as a Service" or SaaS for short. This means that instead of using a normal computer program on a single computer, the software is built and run on the internet. This way an employee can access this software on any computer connected to the internet. This not only saves time, but saves a company money because they don't need to spend as many resources installing and maintaining the software.