I don't know. When my brother was putting the computer together for me, we agreed not to spend any money on sound stuff because I probably wouldn't need it.

Well, now you have me curious. I will search for 'computer jack' and see what it might be.

(okay if you search this page: https://www.computerhope.com/issues/ch001379.htm for "jack", the picture there above it under ports, is that it?)

The circular holes, yes
Otherwise headphones wouldn't have a place to plug in to

"jack" is sort of the semi-official catch-all term for watchamacallems and thingamajigs, isn't it?

There's a car jack and a computer jack and a phone jack and a floor jack and probably lots more I don't know of, but I think it's all from the American English side of the language, isn't it?

Language is interesting. I wonder why Americans like jacks so much?

I have no idea lol
There's also a type of cup called a jack, but I generally see it in middle ages era fantasy books

Whatchamacallit is a candy here

oh! Boot jack, too. That one is England-English, though, I think...

Dafuq is a boot jack

this:


It's a tool/device/thingamajig that you step on one end to hold it in place, wedge your boot into the other and the leverage lets you yank your foot out of the boot.
The second boot is always harder to get off....

you can see fancy ones sometimes made of wrought iron; cricket-shaped ones are probably the most famous.

or simple ones of wood.

Either way!

A thingamabob!

So an unnecessary thing, really
Unless you don't have functioning hands

Mmm, most things are unnecessary when you get right down to it.

Doorknobs, for example.

Or doorknockers!

I mean, I like a fancy doorknocker, I think they're an amazing artform, but they're a bit redundant, wouldn't you agree? You can just knock on the door itself with your knuckles, you don't have to use a knocker.

The knockers I see are usually tiny and decorative
Prolly for the aesthetic lol