The word “tier” is a physical representation (eg sharing layers from one physical project to another ~ it could be in same machine or other).
This means that it can compose your UI, Domain/Business and Data Access or even Services.
If you want to use EF (Entity Framework) then you can use it as your Data Access then have your business/domain in a separate tier to do certain functions related to your business. Your UI can be an MVC/WebForms/Windows apps, etc.. etc...