What I have below is a cell phone photo I took the other day at a local farm stand, springdellfarm.com. I was picking up peaches for my wife who was planning to make a peach crisp.  (I posted the recipe on our cooking blog, here: 
https://essentiallycooking.zenfolio.com/blog/2020/8/peach-crisp

With regard to "vignetting" I've included here a screen shot showing the "before and after", so you can compare. It's subtle but I think it improves things. 

Because I wanted to emphasize the tables full of peaches, I used the Lightroom "brush" tool to darken the corners and edges of the photo and I brought this in toward the table. You can especially see the result in the gravel surface on the left, and the road and cardboard boxes on the right. I did not use the "auto mask" feature. I think of it as vignetting because I am darkening the outer areas of the photo... but this process certainly also fits the definition of dodging and burning.

Before/After
 

I most often use the "radial" tool for making a circular or oval or oblong vignette, but in this case the brush tool let me darken a more defined (and not circular) area.  I darkened the areas outside the table by about .5 stops. 

That was all I had planned to do with the image before posting it on our cooking blog.  But then I thought: why not brighten the peaches a bit.  So I used the brush tool again to brush over the peaches, and I added about .5 stops of exposure. I did use the "auto mask" feature so that the brush would only apply a mask to the color of the peaches.

Vignettes are a great way to focus attention to the main subject of the photo. By darkening areas outside the main subject, it prevents (reduces) those areas from being a distraction.

"Springdell Farm Peaches"
August 25, 2020
iPhone 5S
4.15mm F2.2 lens (about 28-30mm equivalent)
F2.2 - 1/120sec - ISO32