what does the tilday mean

The tilde is a shortcut for your home folder. If, for instance my short user name were toto, the following paths are equivalent:
* ~/Library/Fonts/
* /Users/toto/Library/Fonts/

~/Library/Fonts/ can therefore be accessed by clicking on your home in the sidebar and then navigating to the Fonts subfolder of the Fonts folder...

The ~ character is a general Unix representation for "my home directory", it's not something Apple invented. I've used a dozen or so Unixes over the past 15 years, and they all treat the ~ character the same way. On my Mac, my username is "kaan", and so the full, explicit path of my home directory is "/Users/kaan". However, if I'm logged in as "kaan", I can use "~" to represent "/Users/kaan".

But here's another usage of ~. Say you have an account on my Mac, too, and your username is "kroussin". If I'm logged in, I could reference your home directory by placing a ~ in front of your username (without slashes), like this: "~kroussin".

So if I wanted to copy a file from my home directory to yours, I could do this:
<code>cp /Users/kaan/somefile.txt /Users/kroussin/somefile.txt</code>

or use both forms of tilde shorthand:
<code>cp ~/somefile.txt ~kroussin/somefile.txt</code>

Hope that helps.