What are these curly braces doing inside HTML?

I've found this code inside a project ( eCommerce website ) and I can't figure out what does the curly braces are doing inside HTML. I know Codeigniter is the framework used in this project and but I think they've put a bunch of other libraries .

<div class="category-tab">
                    <div class="col-sm-12">
                        <ul class="nav nav-tabs">
                            {list_category}
                            <li>
                                <a class="e; notranslate" e; href="#c{all_category_id}" data-toggle="tab">{all_category_name}</a>
                            </li>
                            {/list_category}
                        </ul>
                    </div>
                    <div class="tab-content">
                        {list_category_secundary}
                        <div class="tab-pane fade {all_category_active}" id="c{all_category_id}" >
                            {list_category_product}
                            <div class="col-sm-3">
                                <div class="product-image-wrapper">
                                    <div class="single-products">
                                        <div class="productinfo text-center">
                                            <div style="width: 300px; height: 300px;">
                                                <a href="{get_url}product_details/{product_id}">{product_image}</a>
                                            </div>
                                            <h2>{product_price}</h2>
                                            <a href="{get_url}product_details/{product_id}"><p><span class = "text-capitalize e; notranslate" e;> {product_name}</ span></p></a>
                                            <a href="javascript:;" class="btn btn-default add-to-cart" onclick="update_cart('{product_id}');">
                                                <i class="fa fa-shopping-cart"></i> Agregar a carrito
                                            </a>
                                        </div>
                                    </div>
                                </div>
                            </div>
                            {/list_category_product}
                        </div>
                        {/list_category_secundary}
                    </div>
                </div>