question about Orbit sample app todo

Hi list,

I'd like to ask some basic question about orbit sample app - todo.

<body>
<h1>To-do</h1>
<ul id="items">
$items
</ul>
<form id = "add" method = "POST" action = "" '/add' }">
<input id = "title" type = "text" name = "item" size = 30 />
<input id = "button" type = "submit" value = "Add" />
</form>
</body>
</html>
]===]

todo.items = [===[
$if{$items|1}[==[
$items[[
<li item_id="$id"><input class="item" type="checkbox" $if{$done}[=[checked]=] item_id="$id"/> $title
<a href = "" class = "remove" item_id = "$id">Remove</a></li>
]]
]==],[==[Nothing to do!]==]
]===]

This is some part of it.

Let me show you part I don't understand.

$if{$items|1}[==[
................
]==],[==[Nothing to do!]==]

And the part below also.

$items[[
<li item_id="$id"><input class="item" type="checkbox" $if{$done}[=[checked]=] item_id="$id"/> $title
<a href = "" class = "remove" item_id = "$id">Remove</a></li>
]]

There are parts galore which I don't understand..

But If you give me some hint I believe I can understand about orbit..

Thank you very much in advance!

Journeyer