What do you need to know about Service Oriented Architecture?

Question

C++ / C#

Perhaps the question is not too correct, but I'm not at all guided by the topic.
I assume that SOA is popular now and I tried to understand it a little. WCF looks cool: you create a service and access it like a regular class. But somehow too primitive. Therefore, please tell me:
1. what you need to know about SOA and where can you read it?
2. Are load balancing tasks, for example, with a large number of requests, solved by creating many services? Those. we break the integral logic into pieces, maybe even duplicate it? Or am I completely misunderstanding this?
3. what if the service failed? Do we make a dozen duplicates that spin at the same time? Or are services within one application not the right approach, but are they only needed to communicate with third-party resources?
Thank you in advance.