Thank you!

Sorry for the confusion, there is actually some overlap between the words so I'm using redundancy here to mean "If something goes wrong I have an entire extra system" (for example, a second computer or a satellite) and Reliable/Resilent to mean "I have built the computer/satellite in a way which will limit the chance of something going wrong".

So a Reliable system would probably be made up of sub-systems which are themselves redundant (multiple hard drives or solar panels) even if the whole system is not.

I hope this makes sense.