There’s a large variety of knots to allow you to connect terminal tackle to your line, or to join lines together, etc. I learned to tie basic knots from a very young age and I’ve only had a 3-4 knots fail due to being incorrectly tied over the years, no doubt through carelessness. It’s worthwhile having several basic knots mastered to allow you to tackle the basics required whilst fishing.
Years ago you had to sit with a book with poorly animated sketches of how to tie various knots. It was often trial and error until you got the technique right. Below are a couple examples of early instructions, not the best.
There are a couple of good websites out there that provide some excellent animation to enabling you to quickly learn new knots.