A simple answer using CSS is to use the :hover pseudo class on an anchor tag.
Set you image container as position:relative in CSS.
Create a div containing your text, formatted using html and CSS inside the image container. Position this absolute in CSS. Absolute positioning positions elements relative to the parent container positioned relative. If no element is set to position relative it will take its position from the body tag. It is important to set a width to the element too.
THE HTML
<div class="container">
<a><img src="img.jpg" alt="background">
<div class="text">I will show on hover</div>
</a>
</div>
CSS
div.container{position:relative;}
div.text{ position:absolute; top:0; left:0; width:100%; display:none; z-index:10;}
a:hover div.text{display:block;}
This will position the text over the container you set to position relative aligning to the top left corner. The z-index stacks elements one above the other. The higher the z-index the higher the element is in the stack.
w3 schools have some excellent definitions and examples on all the code above if it is new to you.
The effect you are after can be achieved with html and css alone. I would advise you focus on:
- design your site on paper
- layout your page with html and CSS
- add your rollover effects and jQuery animations
before adding the jQuery animation
CSS3 transitions are not compatible with all browsers, there are work arounds in CSS though a jQuery fallback is often used.