what's botstrap? what's w3 Framework? what's difference between botstrap and w3framework?
i don't know learn w3 or botstrap 😟
it's a complement, to the base css. sometimes you need less code, or properties which the base language don't have or it's harder to do, you use a framework. w3 framework it's like the bootstrap one, but more simplified, according to w3 schools itself.
In a daily work with CSS you just need some thing in every project. Simplest example - setting text-align to center. Frameworks are nothing else, but a library of things, that might be needed over and over again, so people don't have to write them each time. They differ in amount of content, style and used technology, so pick one that is most suitable for the stuff you are doing.
Pure vanilla CSS first. And if you'll understand one of them, you can use them all fairly quick afterwards.
animate.css, materialize.css, cutestrap.css