Do wheel adapters add width?
Wheel spacers are used for several reasons, such as adding track width to a vehicle, helping to clear brakes, or to helping alleviate tire rubbing. A wheel adapter is very similar, and it effectively adds width to your vehicle at the same time as a side effect of what it does.
Are wheel spacers the same as adapters?
Wheel adapters do all the same things that spacers do. However, they change the bolt pattern to allow you to bolt up wheels that would not fit without the adapter.