I google’d it and got full-blown essays, so yes, I did do some searching first lol. 
But if someone here could explain it for me in a nutshell, maybe in one paragraph, I’d really appreciate it. A lot of the information kind of confused me to be honest, so I’d be very grateful if someone would be willing to simplify.
Thanks in advance.
I will try and put it as basic as possible:
You put posts into categories to ‘categorize’ them - These are broad topics that you might put a number of different posts under - say you have a sports blog with a posts about Tennis - you would categorize it by putting it into the “Tennis” Category. But with one of your posts, it’s about Tennis, but you want to be more specific - i.e you served an awesome serve, or i.e you have sprained your ankle - then you would tag it - “serving” and “injury” and “ankle” etc. This means that while people browse your blog, they can see at a glance what each post contains under each category.
Hope this makes sense.
Do you recommend using tags? Does it really matter?
If you have to ask that question, then it probably doesn’t. You’ll know when you want them, though, and when that time comes, they’ll be available.
I think it is worth using tags. It makes the way people see your posts while browsing your site easier to see the specific of said post. It also should provide better SEO for your site (someone in the know of SEO will need to confirm this).
Basically, tags take you all of 1 minute to enter, and they are no harm to your site, so I say you might as well. But if you don’t want to, don’t bother. It’s up to you.
In that case, I’m probably best off using them. Thanks, guys.