Why width CSS attribute of label doesn't work without float?

Why width CSS attribute of label doesn't work without float?

I'm new in CSS, and I've got one question. I'd like to make a good simple
form, and there is the following code:
<form>
<div class="row"><label for="name">Some text field</label><input
type="text" name="name" /></div>
<div class="row"><label for="surname">Some another text
field</label><input type="text" name="surname" /></div>
</form>
Some CSS code:
label {
float: left;
width: 230px;
text-align: right;
margin: 5px;
}
.row {
clear: left;
}
I copied and pasted this code from some book. I understand floating,
clearing, but I don't understand why does "width" attribute work with
label (because it inline element) and, in this case, why doesn't "width"
work without "float"? Please, make me clear. Thanks