In Bootstrap what is "wells" exactly?

Question

In W3schools I love to roam around the codes and learn the different coding languages I've lots of questions their but my first one I really wanted to know what's "wells" exactly is it a good way to make like a layout sheet here is the website code link
https://www.w3schools.com/bootstrap/bootstrap_wells.asp so like for an editing image program like Photoshop/gimp etc.. I use gimp but how do I extract my edit image to put on my website and what template size should I use because I've no clue how to do that?

Answer 1

A well is a container in <div> that causes the content to appear sunken or an inset effect on the page. To create a well, simply wrap the content that you would like to appear in the well with a <div> containing the class of .well.