Edit in JSFiddle

$('#staff_onglets').on('mouseenter', '.onglet', function(){
    if ($(this).hasClass('active')) return;
    
    var $onglet = $(this),
        $onglets = $onglet.parent().children(),
        $contenus = $onglet.parent().next().children(),
        index = $onglets.index($onglet);
    
    $onglets.removeClass('active');
    $contenus.removeClass('active');
    
    $onglet.addClass('active');     
    $contenus.eq(index).addClass('active');
});

<div class="onglets_container" id="staff_onglets">
    <div class="onglets_survol">
        <div class="onglet active">
            <img src="http://i39.servimg.com/u/f39/18/99/93/58/0110.png" />
        </div>
        <div class="onglet">
            <img src="http://i39.servimg.com/u/f39/18/99/93/58/0210.png" />
        </div>
    </div>
    <div class="onglets_contenus">
        <div class="onglet_contenu active">Contenu 1</div>
        <div class="onglet_contenu">Contenu 2</div>
    </div>
</div>

.onglets_container {
     text-align: center;
     width: 210px;
    
}
.onglet {
    display: inline-block;
    margin-right: 10px;
}

.onglets_contenus {
    background-color: #575d44;
    border-color: #bbcc78;
    border-style: solid;
    border-width: 2px 1px;
    color: #bbcc78;
    height: 70px;
    padding: 5px;
    width: 200px;
    margin: auto;
}
.onglet_contenu {
    display: none;
}
.onglet_contenu.active {
    display: block;
}