How can I easily hide / display a form or text on my website?

Here's a simple example of turning on a hidden form / paragraph using javascript.

<a href="#" onclick="document.getElementById('show_car').style.display = 'block';">Show Car</a>

<p>

<span id="show_car" style="display: none;">

This is my car.

</span>

</p>

This is a simple example, clicking the link just shows the data - but it can easily be expanded on to be a toggle switch, and show much larger chunks of content.