SOA is a design pattern in which services are provided between components, through a communication protocol over a network.
Microservices are an architectural style that structures an application as a collection of small, autonomous services. Each microservice is self-contained and exposes a business capability, which is implemented by an object (i.e., OOP).
The concept of "Everything as a Service" (XaaS) extends the principles of SOA and microservices by offering comprehensive services over the internet. XaaS encompasses a wide range of services, including infrastructure, platforms, and software.