For a 3D printer to work there are 3 things which are needed
Design Software
This is used to create models that are to be 3D printed (you create the design) or you can access models that are already designed from many online sources like Thingiverse or GrabCAD
Firmware
Firmware is what allows the printer to read the sliced file and print the object. This is a part which will 99% of the time come with the printer and you will not need to do anything.
Slicing software
This is used to convert a 3D object that was created in the design software or from a downloaded file into what is called a G-Code file (a.k.a GPS for the 3D printer). This file allows for objects to be 3D-printed. Some common slicing softwares are CURA or Slic3r
