Regular Expressions - Remove Whitespace from Start and End

I do not completely understand regex characters :“+” ,“$”.
What do the above characters imply in the code? please clarify for me i get confused on what their purpose is.

Your code so far

let hello = "   Hello, World!  ";
let wsRegex = /\s \s \s/g; // Change this line
let result = hello.replace(/\s/g, ""); // Change this line

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Challenge: Regular Expressions - Remove Whitespace from Start and End

Link to the challenge:

$ follows the character that must be on the end of the string
+ follows the character for which there must be 1 or more

$t matches the ‘t’ in ‘eat’ but not ‘eating’
e+ matches ‘ee’ and also ‘e’ and ‘eee’