Soldering is somewhat tricky especially when you need to solder two components and wires together.
In practice you'll need a tool called a "helping hand", to assist in the soldering process. It's job is to hold and align the components or wires that need to be joined, freeing up your hands to hold the soldering iron and the solder.
If you have actually tried this, you'll find that the whole process is quite cumbersome, especially the process of aligning the components or wires just right (making sure the leads are making proper contact) before you can apply the solder.
This is where the Fixed Iron Method comes in. It allows for a quick and easy way to solder wires and electronics components together.
Having the soldering iron fixed in-place frees up your hands, allowing better control and much more consistent results.