Well this was frustrating and I'm glad I've got it solved.

I have a computer that I want to use as a server and tuck it away in a closet and just leave it unattended but keep it available for incoming connections. 

What I learned is that networking, including WiFi, completely doesn't work on Ubuntu (Mate edition, and probably others) unless a user is logged in. That is, the network is completely down on this Ubuntu computer until a person logs in. 

As a server, that's not a good thing because I want to run backups automatically and have other servers automatically log in to this Ubuntu system in the wee hours of the morning. 

Luckily all I had to do to get it so that networking, and WiFi, start automatically at boot is the following:

First I navigated to /etc/NetworkManager/system-connections/

Second I found a file in that directory that has the same name as my WiFi connection ssid. 

Third I opened the file with sudo and I found a line that said "permissions=user:myusername:;"

Fourth I removed everything in that line after the "=" so that it just said "permissions="

Fifth I rebooted my computer

After I rebooted, I was able to connect to the computer remotely so that meant that the network was started even though I hadn't logged in. That made me happy because that's exactly what I wanted it to do. 

Here's where I found out how to do this. askubuntu.com/questions/16376/connect-to-network-before-user-login There's some other information there which might be useful.