Service Oriented Architecture (SOA) is a way of designing systems so that they are composed of smaller discreet systems that can be connected to when needed and therefore promotes re-use. This is by no means a new concept, but SOA does more to help with connecting systems wherever they are and to many SOA is an architectural vision rather then various technical components frequently mentioned alongside it. The term SOA, at least, has disappeared somewhat off the scene since 2015 or so, but the principles continue strongly.
The “Explained series” is planned to build into a trustworthy collection of explanations and commentaries that can be trusted to tell the story straight without any bias and attempt to make the subjects accessible to the layman. The latter is not always easy as some of these terms refer to genuinely complex subject matter, while others are simply too vague to pin down (there’s another word for that).
If you want an answer on something and you can’t find it easily, please use the comments section to just ask and I will appreciate not having to research the next topic.