In regular expressions "+", "*", "." What is the difference between [] within and outside? Non-escaping

For example:

[\w.]+和[\w.+*?]

What is the difference between these symbols in [] and the outside?

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For example:

[\w.]+和[\w.+*?]

What is the difference between these symbols in [] and the outside?

First [] , the contents of the regular expression represent the meaning of the optional combination,
Similar

/[\w.]/.test("a"); // true/[\w.]/.test("."); // true/[\w.]/.test("a."); // true/[\w.]/.test(" "); // false

The optional combination of the above regular expression can match a character, or a dot, but cannot match the null character;

Tell me the difference:
1. . in [] the inside, it is to match . , in the outside when it is used to match any character, see the following example:

/./.test(" "); //true/[.]/.test(" "); //false

2. * and + on the [] outside is called the quantifier (quantifier of the quantity word), is to indicate the quantity to match,
*Represents any number, which is represented by a set [0, +00) ;
+Represents at least 1 times, the set represents Yes [1, +00) ;
It has to be said that, as a quantifier, * and the + preceding must follow the meaning of the regular expression (part);
Within it means the [] meaning of itself, in order to match * or + ;

/[+]/.test("+"); //true/+/.test(""); //Uncaught SyntaxError: Invalid regular expression: /+/: Nothing to repeat(…)/.+/.test("oops"); //true

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