i>modifier keys</i> to change what happens. Holding down a modifier key while clicking will control how the selection is affected:
</p>

<dl class="org-dl">
<dt><b>Shift+click</b></dt><dd>Holding the <b>Shift</b> key while clicking will <b>add</b> whatever is clicked to the selection, without unselecting what was selected before.</dd>
<dt><b>Control+click</b></dt><dd>Holding the <b>Control</b> key while clicking will <b>invert</b> membership of the selection, without changing the rest of the selection. For 