Actually, you are raising the temp of the contents of the jar, all the way through, and you are removing the air and sealing the lid.
You definitely don't want to overdo it or you will overcook whatever you are canning. Kinda like boiling pasta way too long, it will be yucky.
If I could offer you any advice, I think the most valuable would be to keep your canning to one or two things a growing season, until you pretty much master the art of water bath canning are are comfortable with what you're doing. Confidence in what you're doing really goes a long way with canning.
I learned to make jelly and jam from the instructions on a box of Sure Jell. In fact, I keep one of those instruction sheets taped to the inside of a cabinet door by my stovetop. Helps me check ratios of juice and sugar for fruits. If the particular fruit isn't mentioned, I choose something similar.
Taught myself the art of pickles from an old worn recipe on a brown piece of paper that my husband's grandmother wrote back in the 40's. It took me a couple of years to get it right, but I have gone on to pickle just about anything I can get my hands on.
Now I ventured deep into pressure canning stuff. I'm getting ready to put up some sweet potatoes ... got 80 bushels of them to feed deer, but they are too pretty for the deer to eat them all. Then I have some turnips to do.
This was my second year doing canning, so I had added about three things. The pickles I did last year I did only as refrigerator pickles, no worries with that of course.
And I hot pack the pickle jars, so I wonder if that affects the canning time?
The jars I put into the fridge always seal on their own. I’ll get it figured out. :) I think my stove is a big player in this too - it’s an ancient electric stove with horribly uneven heating elements.
The jelly just takes a bit more focus on my part, I’m not too worried about that now. (Sure-jell box here too) Taught myself what not to do right along with what works this year. Mostly with the whole “sheeting” thing - takes a practiced eye - and I got panicky about it this year, LOL.
I may try to pressure can one thing this year. I might wait though until I work the bugs out of my water bath efforts. We’ll see how it goes. I feel very determined to get it right.