I don't understand the tree of projects and stuff works in the top left of the VBA editor window.

It appears that I am accidentally linking my macros in some way... and I don't understand how or why it does this, and what you are supposed to do - because I'm obviously not doing it right!

I edit a macro and I have one set of stuff under a bold heading here.
I open a second macro for editing. I don't get a new instance of a separate VBA editor, I get a second tree of stuff I don't understand the workings of, in this window. I can swap between the two macros and edit them.

What I cant seem to do is save and close just one of them, or save just one of them to a new *. swp name

I am obviously missing some basic fundamental understanding here...

I may have inadvertently linked more than one macro SWP file here, perhaps into a single project? how do projects relate to separate swp files? nothing I can find explains that...

To my dismay/horror I find opening some of my swp files for editing from a new session, and  I have several trees of stuff in this window, and I can open different windows of completely different code that is nothing to do with what I'm doing and I though was contained in totally unrelated swp files... I opened one swp file. why is code from the swp file I opened last month showing?  I fear I have destroyed one of my working macro swp files accidentally when it might have been editable without me intentionally opening it.

I can find no explanation of how this tree structure works, and how it relates to separate swp files, how to purge it of the stuff I don't want there? if I have opened several macros swp files in this window, how to save and close one without affecting the others.

Has anyone got a link to a simple (from zero knowledge of vba) explanation of how this window (and the other windows) work? and how they relate to separate swp macro files?