Play Framework Scala Template

I've worked around with Play Framework for a while but I'm almost new to Scala Templates . For me as a C-familiar language developer sometimes it looks a bit strange

I was wondering if someone here could help me understand this code better I took it from http://www.playframework.com/documentation/2.2.x/JavaGuide3 (Zentask Example)

@(projects: List[Project], todoTasks: List[Task])

@main("Welcome to Play") {

    <header>
        <hgroup>
            <h1>Dashboard</h1>
            <h2>Tasks over all projects</h2>
        </hgroup>
    </header>

    <article  class="tasks">
        @todoTasks.groupBy(_.project).map {
            case (project, tasks) => {
                <div class="folder" data-folder-id="@project.id">
                    <header>
                        <h3>@project.name</h3>
                    </header>
                    <ul class="list">
                        @tasks.map { task =>
                            <li data-task-id="@task.id">
                                <h4>@task.title</h4>
                                @if(task.dueDate != null) {
                                    <time datetime="@task.dueDate">
                                        @task.dueDate.format("MMM dd yyyy")</time>
                                }

                                @if(task.assignedTo != null && task.assignedTo.email != null) {
                                    <span class="assignedTo">@task.assignedTo.email</span>
                                }
                            </li>
                        }
                    </ul>
                </div>
            }
        }
    </article>
}

This 3 lines are really confusing for me :

@todoTasks.groupBy(_.project).map {

case (project, tasks) => {

@tasks.map { task =>

I do appreciate if anyone can explain me in more details what exactly these 3 lines are doing?

Thanks guys