When we really need to encoding URL since we can easily decode it using decoder?

Question

"URL encoding replaces unsafe ASCII characters with a "%" followed by two hexadecimal digits."
What's the meaning "unsafe ASCII characters"?
could u give more additional explanation about "inject code via the URL" related to encoding URL?
Please give real sample when we really need to encoding URL.

Answer 1

Cross-site scripting (XSS) is a thing.
https://en.m.wikipedia.org/wiki/Cross-site_scripting
Also, things like whitespace have to be represented as a %20, because URLs can't have whitespace.

Answer 2

So anyone with even basic skills wouldn't be able to just inject code via the URL.