Is there any difference between:

.x1 {color: black;}

.x2.x3 {color: green;}

.x1.x2.x3 {color: red;}

and

.x1 {color: black;}

.x2, .x3 {color: green;}

.x1, .x2, .x3 {color: red;}

lets say:

<p class="x1"></p>

<p class ="x2 x3"></p>

<p class ="x1 x2 x3"></p>

Just wondering...