The Swagelok company has some descriptions of connections. I think it makes more sense to look at their online manuals than to try and explain how the connector body, ferules and retaining nut work.
Their PFA Tube Fittings Catalog is
www.swagelok.com/en/spec/pdf/MS-01-05.pdf This gives a detailed description of their fittings. There is an installation guide which gives an explanation of how to seal the connectors at
www.swagelok.com/en/jhtml/UIGuides.jhtml%3FS=18&request=?_requestid=37190
The best picture is on page 6 (of a 1 MB pdf file).
The units from McMaster Carr work the same way.
These connectors are for hard, thin walled tubing. One disadvantage of this is that is pretty hard to get a sharp radius. SO, you may need to get some elbows to navigate the inside of your case. This would be one place that I am thinking about getting some of the plastic elbows ( I don't want a metal block near a motherboard)
I am getting some components together & I will try to get some pictures and get some good written notes.