Pat wrote:
I'm using Windows 10 1809. Twice today, Skype showed up in the tray.
There doesn't seem to be an exit command in the menus - just a "hide".
I knew Skype was installed, but I almost never use it. I can't find
what is starting it up. If I open it and then kill it with task
manager, it goes away but then comes back later. Any ideas why this
started happening today?

Pat

Check your Task Scheduler.

Start : Run : control
Pin the Control Panels on the task bar.
Find the Task Scheduler and have a look around.

Microsoft has a weird sense of humor. If you install
some other Microsoft software, say "Outlook 2019" to make
up an imaginary tool, they may want to show your Skype
status as "available" when you enter Outlook. They may have
integration features that detect your presence and make
you visible to other Skype users. To support such behaviors,
perhaps the new software you installed, added a Skype rule
to keep it awake.

Paul