3D modeling is the use of software to create a virtual three-dimensional model of a physical object. 3D models can be used in video games, animation, as part of Computer Aided Design and Manufacturing, or for 3D printing, among other things.
3D modeling can seem daunting but if you can use a computer you can start modeling useful things right away. The learning curve is long, but it isn't that steep.
There are many free 3D modelling software options available online. This list highlights some of the excellent programs that are available.