Edit Categories, Tags Front End

First, sorry for my bad english!

Hi, I’m trying create a page to edit categories, tags and custom taxonomies front and. But can’t find the correct function to update fields on submit.

The code:

<?php

/*Template Name: Page Template Editar Cetegoria*/
get_header(); ?>

<section class="conteudo-geral">
<section class="conteudo" style="width: 990px" role="main">

<?php
$pid = $_REQUEST [ 'pid' ];
$taxonomia = get_term_by('id', $pid, 'category', 'ARRAY_A');

$nome_taxonomia = $taxonomia->name;
$descrição_taxonomia = $taxonomia->description;
?>		

<form action="" method="post">

<tr class="form-field form-required">
<th scope="row" valign="top"><label for="name">Nome</label></th>
<td><input name="name" id="name" type="text" value="4Cast" size="40" aria-required="true">
</td>
</tr>

<tr class="form-field">
<th scope="row" valign="top"><label for="description">Descrição</label></th>
<td><textarea name="description" id="description" rows="5" cols="50" class="large-text"></textarea><br>
</td>
</tr>

<p class="submit"><input type="submit" name="submit" id="submit" class="button button-primary" value="Atualizar"></p>
</form>

</section>
</secrion>

<?php get_footer(); ?>