A question on CSS selector syntax

I have a question on CSS selector syntax.

What is the difference between the following two CSS selectors?

.myclass1 .myclass2 {
    color: black;
}

.myclass1.myclass2 {
    color开发者_StackOverflow中文版: black;
}

Are they the same?

Thanks.

.myclass1 .myclass2: select the element that has the class "myclass2" inside another element of class "myclass1";

.myclass1.myclass2: Select the element that have both class.

.myclass1 .myclass2 will match the inner DIV in

<div class="myclass1">
    <div class="myclass2"></div>
</div>

.myclass1.myclass2 will match

<div class="myclass1 myclass2"></div>