A typical software application is a bit like an iceberg. As a user, you can see some portion of application, but in most cases a larger massive part of it remains completely invisible. This is basically 'back-end' as it is.
All data must be stored somewhere and, if necessary, retrieved. Business logic and rules must be followed and results must be calculated. Usually it is a backend developer who is responsible for getting access, reading and rendering data. Also having skills like SQL in this area of work can be extremely important.
What back-end developers do depends on the project and can vary a lot, according to the scope specifics and requirements. But in most cases front-end specialists are busy by building the user interface and back-end engineers are involved in coding that makes it all work. Thus, in the world of web development most of the back-end developers are concerned with the creation of logic that will actually make application work.
Additionally, back end developers must also work well with server-side languages for the technology stack use.
In order to be worth, a good background developer should have different platforms and libraries understanding, experience in integrating of it into a single elegant application and structurising entire business logic to make the system become easier to maintain.
ZubrSoft puts great efforts into attracting these kind of talents onboard, so our customers will get an easy access to the software engineers with knowledge of the most important back-end technologies and frameworks.