Hello all!
My name is Lorraine and I'm brand new to Gimp although I've had it on my laptop for a while and have collected tons of products that work with Gimp. I currently have version 2.10.36 and I have been practicing for the last few days with "Getting Start with Gimp" videos from several channels until a few hours ago. When I was following a video that walked you through creating a poster for a cookie company. Everything was going great until I got to the part in which you resized the second image of a stack of cookies. For some reason I could not get it to resize the correct image. It will only pick and resize the background image and not the new one that I brought forward. I tried to find a cause. I tried backtracking to right after I resized the first image but when I'd click the eye icon so that the next image is visible and then click the resize tool it resizes the background image [the first image I resized. Clicking the image doesn't work and choosing the select causes the image to duplicate and you end up resizing what you think is your image but you're actually resizing one of the duplicates which then resizes to the smaller duplicate image size. I even tried closing out the original, deleting that file and restarting the project over again but now I can't get Gimp to resize any image I upload including the first image that I was originally had no problem resizing. I was wondering if anyone can tell me if perhaps, I have locked something by mistake that would cause this kind of issue?

Hi Firestarter. Left-clicking a layer selects it and it becomes the active layer. This is the one you work on mostly. (mostly because you can also link layers. )
Layers and frames are terms for the same thing.
Like all new things it can be frustrating but I guess that's the learning process.

Welcome to Gimp Chat, Lorraine.
It could be that without realizing it you had pressed another icon that does not correspond to layers. For example the routes icon. This would cause the action you want to take to not respond.
Try to put the tools back to their initial state. That will restart everything again.