Applicators are designed to make it easy to apply product with control, without making a mess on your hands.  You can apply most products with a microfiber cloth, but it is hard to stop getting product onto areas you don't want it, like not getting wax on plastic trim etc, and you normally have it soak through and onto your fingers, which you then need to clean along with all the things you touched.  Applicators are way easier cleaner and faster.  If you look after them, they last ages.  Color codes to not mis them up, you don't want to get residue tyre shine on your leather seats.  

We have three main types of applicators, the wave is designed for Tyres and plastic trim, it has 2 types of foam to stop liquid soaking through to your fingers, and a wave like pattern to push product into the ripples on Tyres so you get a quick easy full coating even over the lines and bumps and markings.  

The foam round looking applicators are the most basic and work fine well.  they are often called UFO's.

The microfiber covered foam applicators like the roadie are the most popular applicator.  the microfiber has a few advantages, it allows you to have different colours, it allows you to machine wash them without them falling apart and getting foam all through the wash, and they are soft (well the ones we sell are, especially the roadie with 73:30 blend and high quality made in Korea).  Thats what I tend to use mostly, though I use the wave on wheels.