Basically, say you have checkboxes like so:
<input type="checkbox" name="id[]" value="12">12<br/>
<input type="checkbox" name="id[]" value="123">123<br/>
<input type="checkbox" name="id[]" value="1234">1234<br/>
and let's say you check all three and then submit the form.
Now, $POST['id'] isn't a string, but rather an array. As such, you can loop through it and retrieve the multiple values that were submitted:
foreach($_POST['id'] as $id) {
echo 'You checked ID#: ' . $id;
}
The most common applications I can think of are checkboxes with the same name (as I illustrated in my example) or a SELECT form entity that allows multiple selections:
<select multiple="true" name="id[]">
<option value="12">12</option>
<option value="123">123</option>
<option value="1234">1234</option>
</select>
EDIT: Also, a note about Htmlwiz's reply: Array indeces in your case should be strings. $row[name] does not have a string as an index, but a constant. PHP will detect this (assuming there actually isn't a constant named 'name') and throw an E_WARNING and then assume it is a string. So, use quotes: $row['name'].
EDIT: In addition, though I sort of explained it by example, I just want to say it to make it clear: The only change in the HTML code you must make to turn a group of elements into an array is add brackets ( [] ) onto the end of their names.