ListBoxItem represents a selectable item in a ListBox.
Example
<Window x:Class="WpfApplication3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ListBox HorizontalAlignment="Left" Height="100"
VerticalAlignment="Top" Width="100">
<ListBoxItem Content="1"/>
<ListBoxItem Content="2"/>
</ListBox>
</Grid>
</Window>