An example of different ways to code the Umbraco FAQ Package's content.

FAQListing.cshtml

@using FAQ
@inherits UmbracoTemplatePage
@{
    Layout = null;
}

<h1>@Model.Content.Name</h1>

<h2>Render All FAQ Items</h2>

@if (Model.Content.HasProperty("faq") && Model.Content.HasValue("faq"))
{
    <ul>
        @foreach (var q in Model.Content.GetPropertyValue<FAQListing>("faq").Items)
        {
            <li>
                <h3>@q.Question</h3>
                @q.Answer
                <p>
                    Categories:
                    @foreach (var category in q.Categories)
                    {
                        if (category != q.Categories.FirstOrDefault())
                        {
                            @(string.Format(", {0}", category))
                        }
                        else
                        {
                            @category
                        }
                    }
                </p>
            </li>
        }
    </ul>
}

<hr />

<h2>Render FAQ Items By Category</h2>
@if (Model.Content.HasProperty("faq") && Model.Content.HasValue("faq"))
{
    var categories = Model.Content.GetPropertyValue<FAQListing>("faq").Categories;
    
    <ul>
        @foreach (var category in categories)
        {
            <li>
                <h3>@category</h3>
                @if (Model.Content.GetPropertyValue<FAQListing>("faq").Items.Any(x => x.Categories.Any(y => y.Contains(category))))
                {
                    <ul>
                        @foreach (var q in Model.Content.GetPropertyValue<FAQListing>("faq").Items.Where(x => x.Categories.Any(y => y.Contains(category))))
                        {
                            <li>
                                <h3>@q.Question</h3>
                                @q.Answer
                                <p>
                                    Categories:
                                    @foreach (var cat in q.Categories)
                                    {
                                        if (cat != q.Categories.FirstOrDefault())
                                        {
                                            @(string.Format(", {0}", cat))
                                        }
                                        else
                                        {
                                            @cat
                                        }
                                    }
                                </p>
                            </li>
                        }
                    </ul>
                }
            </li>
        }
    </ul>
}

<hr />

<h2>Render FAQ Items by Querystring</h2>
@if (Model.Content.HasProperty("faq") && Model.Content.HasValue("faq"))
{
    var category = Request.QueryString["category"];

    var questions = !string.IsNullOrEmpty(category) ? Model.Content.GetPropertyValue<FAQListing>("faq").Items.Where(x => x.Categories.Any(y => y.Contains(category))) : Model.Content.GetPropertyValue<FAQListing>("faq").Items;
    
    if (questions.Any())
    {
        var count = questions.Count();
        if (count > 1)
        {
            <p>There are @count questions that match your query.</p>
        }
        else
        {
            <p>There is 1 question that matches your query.</p>
        }

        <ul>
            @foreach (var q in questions)
            {
                <li>
                    <h3>@q.Question</h3>
                    @q.Answer
                    <p>
                        Categories:
                        @foreach (var cat in q.Categories)
                        {
                            if (cat != q.Categories.FirstOrDefault())
                            {
                                @MvcHtmlString.Create(string.Format(", <a href=\"?category={0}\">{1}</a>", cat, cat))
                            }
                            else
                            {
                                <a href="?category=@Html.Encode(cat)">@cat</a>
                            }
                        }
                    </p>
                </li>
            }
        </ul>
    }
}