In WordPress, a theme is a collection of templates and stylesheets used to define the appearance and display of a WordPress powered website.
You can see what theme you have by logging into your WordPress account. Go to Appearance -> Theme. You will see a square with your theme that says active: (theme name)
For me my theme is 30 Day Blog Challenge.
Double check to see that you have only 1 theme active at a time. If there is another theme next to it (like mine has Theme: Twenty Seventeen (however it is not active. It has a button that says activate). If there isn’t a second square with a theme in it (that’s okay too).
Hope this makes sense. Let me know =)