Photoshop Elements 14

Photoshop Elements 14 has begun running so slowly that it's almost impossible to edit a picture sometimes.  I'm trying to figure out what caused it to slow down.  I have never imported photos into the program except the ones I edit.  When I opened the organizer to see if there were a lot of pictures that might be slowing things, I found a lot of them there.  So...questions! 

Are the actual photos stored in the organizer?  Or is it just a path to the photos that are stored on an external drive? 

If they are actually stored there, how do I remove them and how do I prevent future pictures from being stored?

What can I do to improve the speed of the program?  It has become ridiculously slow!

Thank you for any help you can provide!