3D Modeling involves a wide number or processes, and understanding your options will help you decide the best choice for you.
I have worked mostly with Blender and TinkerCAD for a variety of reasons. I do have some experience working with Fusion 360 from when I took an MIT course on Additive Manufacturing. I will go into detail about each of these in later posts. Because there are many options out there to chose from, I recommend chosing something with a large amount of community support, and learn that one really well.
There are other programs that you will use to take 3D scans and move them into a modeling program. More detail about those in the 3D scanning posts in that Category.
The last element tied to 3D modeling is slicing. THere are a variety of slicers to choose from. The slicer takes the settings you provide and creates gcode for a specific printer. The printer then takes that gcode and prints the model you chose. I will discuss different slicers in the 3D Printing category.