My mum has been diagnosed with this, what is it?

What is cryptogenic fibrosing alveolitis ?

I am NOT a doctor.
This is NOT medical advice.
This is understanding the words that make up the phrase.
1) cryptogenic, adjective.(of a disease) of unknown origin; obscure.
2) fibrosis, noun.excessive growth of fibrous connective tissue in an organ or part of the body.
3) alveoli (air sacs) of your lungs.

The common name for this is Idiopathic Pulmonary Fibrosis

Here is a very friendly site that describes it.

Idiopathic Pulmonary Fibrosis | Health | Patient UK

Thank you for your replies, the website you suggested was most helpful.