I heard that you have to pay it, but
what if I am 18 years old dude who has
no idea how to pay taxes?
Old man shaking a stick and shouting at the clouds: “I blame the education system!” I bet you know a lot about 18th century Slovakian poetry, though, right?
I mean let’s say I would earn 120€ in
a month (In my dreams) do I really
need to pay taxes?
Yes and no! In most countries there is a certain amount that you can earn that is tax free. 3,803€ - personal allowance in Slovakia according to the Wiki, for example. If you earn less than that in a year, it’s all yours to keep. Although other fees may apply.
Only when you start earning more, you need to pay more (and more) taxes - it’s usually organised into brackets.
But if you’re earning any money, you still need to register than income. If you’re self-employed and / or run your own company, you tell the taxman how much you’ve made in total last year (you may have more than one source of income) and they will tell you how much you owe them (in many cases it will be up to you to figure out how much you owe them :|. They will chase you up if you over or underpay.
If you made little, below the threshold, you may not owe any tax whatsoever.
This will depend heavily on the country. Ask in Slovakian gov forums, ask teachers, parents, a business(wo)man they know.
Tax fraud is a thing, don’t underestimate this. People do get in trouble for tax evasion: