Make Bootstrap Carousel Dynamic - Laravel 5.3

gistfile1.txt

<div id="carousel-example-generic" class="carousel slide" data-ride="carousel">

                <!-- Indicators -->
                <ol class="carousel-indicators">
                    @foreach( $trip->photos as $photo )
                        <li data-target="#carousel-example-generic" data-slide-to="{{ $loop->index }}" class="{{ $loop->first ? 'active' : '' }}"></li>
                    @endforeach
                </ol>

                <!-- Wrapper for slides -->
                <div class="carousel-inner" role="listbox">
                    @foreach( $trip->photos as $photo )
                        <div class="item {{ $loop->first ? ' active' : '' }}" >
                            <img src="{{ $photo }}" alt="{{ $trip->listing->name }}">
                        </div>
                    @endforeach
                </div>

                <!-- Controls -->
                <a class="left carousel-control" href="#carousel-example-generic" role="button" data-slide="prev">
                    <span class="glyphicon glyphicon-chevron-left" aria-hidden="true"></span>
                    <span class="sr-only">Previous</span>
                </a>
                <a class="right carousel-control" href="#carousel-example-generic" role="button" data-slide="next">
                    <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
                    <span class="sr-only">Next</span>
                </a>
            </div>

what does the $loop->first mean because that part is confusing me