Edit in JSFiddle

var UserModel = Backbone.Model.extend({
    defaults: {
        name: "Pablo",
        age: 32
    }
});

// Create an instance of the UserModel with our own info
var JorgeModel = new UserModel({
    name: "Jorge",
    age: 45
});

var UserView = Backbone.View.extend({
    // Set the element to which we attach our view
    el: "#userList",
    // Set up our template
    template: _.template($('#userTemplate').html()),
    // Initialize our view
    initialize: function () {
        // Listen for changes to the model and render the view
        this.listenTo(this.model, "change", this.render);
        // Render the view to start
        this.render();
    },
    // Render the view
    render: function () {
        // Set the the rendered view to the view’s element
        this.$el.html(this.template(this.model.attributes));
        // Return this (used for chaining)
        return this;
    }
});

// Create an instance of the UserView with our JorgeModel
var JorgeView = new UserView({
    model: JorgeModel
});

<ul id="userList"></ul>

<script type="text/template" id="userTemplate">
    <li class="user">
        <p><%= name %> is <%= age %> years old</p>
    </li>
</script>