What is "id" in this code? [html]

[Nik_s3]

Hi, is someone that could explain to me what is the role of this part of code?

<label for="cb_rules_agree"><input type="radio" name="agree" id="cb_rules_agree" value="1" /><strong><phrase 1="$vboptions[bbtitle]">$vbphrase[read_agree_abide_by_rules]</phrase>

cb_rules_agree is only a label that doesn't have effects on the code?

What does It change if I delete this:

<label for="cb_rules_agree"><input type="radio" name="agree" id="cb_rules_agree" value="1" /><strong><phrase 1="$vboptions[bbtitle]">$vbphrase[read_agree_abide_by_rules]</phrase>

Thank you.