DXA requires installation of the following SDL Web Software components :
- Content Manager
- Experience Manager
- Content Data Store
- Content Service
- Deployer Service
- Context Service
- Discovery Service
But why does DXA require XPM to be installed?
Experience Manager doesn’t have to be installed, but DXA has built-in support for XPM. This obviously won’t work if you don’t install XPM.
But, again, it is perfectly possible to use DXA without XPM.