Facebook Auto-Generated Preview TExt

Hello! I’m sure this has already been previously answered, but I’ve spent a few hours perusing the forums and haven’t been able to find the precise answer for my problem. I’ve used about 6 different cache clearing plugins but I can’t figure this out. I’m also new to WP, so the answer is probably pretty obvious.

When I type out my link to share it on Facebook, I get this as the auto-generated preview text: https://ascienceenthusiast.com/wp-content/uploads/2015/04/32432.jpg

I’d like for it to be just an “about” the page, not necessarily a post. But more to the point, the post it’s referring to doesn’t even exist on my page (I re-did it as an intro post). I’ve noticed that when I change the title of other pages, it doesn’t update the preview text as well, even after I completely deleted and re-made the page.

Can someone tell me what I’m doing wrong here? Thank you! ??