There are many different diffusers available, with a few basic types on the market. Electric or battery powered diffusers will break the oils into nano-particles and push them into the air. The aroma fills the air and everyone in the room receives the benefits from just breathing.
A nebulizer style diffuser is most common and is used by adding water and anywhere from 2-15 drops of essential oil, depending on the capacity limitations for that diffuser. Consider the size of the room when deciding on a diffuser, and the stated run-time.
A waterless diffuser is great for filling a larger space with the essential oil aroma. These tend to use oils more quickly and make blending more difficult. Consider the number of adjustable settings to more easily control the amount of oil diffused and for how long.
Personal diffusers are smaller and often have USB plugs. These are great for diffusing in a small area to benefit an individual. Personal diffusers can also be in the form of diffuser jewelry, often used by adding essential oils to lava rocks, leather or felt pads components of the jewelry.
The dōTERRA diffusers do perform exceptionally well, including the Petal, AromaLite, and Lumo.