Keyring?

I'm new to Linux and a bit lost with some of the vernacular. I'm working my way through the getting started and in section 3.7.1, step 4 it states:

.4. Add the LinuxCNC Archive Signing Key to your apt keyring by downloading [the LinuxCNC installer script]( www.linuxcnc.org/linuxcnc-install.sh ) You will need to make the script executable to run it:

What is an Archive Signing Key
What's a keyring, and where is it located? 

So I clicked the link, the file was downloaded to jeff/home/Downloads.

Then I typed "chmod +x linuxcnc-install.sh"

 

$ chmod +x jeff/home/Downloads/linuxcnc-install.sh

Or better yet
$ cd jeff/home/Downloads/
$ chmod +x linuxcnc-install.sh
 

The keyring is a metaphorical collection of metaphorical keys.
In this context the keys are cryptographic keys used to validate the source of software downloads, to ensure that nobody is sending you something other than what you asked for. (for example, being sent a bitcoin miner called linuxcnc rather than the real linuxcnc)

You should probably look at the contents of the installer script and satisfy yourself that you are happy with what it is doing.
(I wrote the script)

You can see inside the script that the keys are installed in /usr/share/keyrings/