They are decorations made as frescoes or acrylic wall paintings or simply paintings on panels which are meant to create the illusion of wider spaces, or inexistent rooms, windows, plants...
They are used to decorate, enlarge, furnish spaces and rooms, which are difficult to resolve for their particular architectural feature. For example passages, blind windows, walls...
If you are very clever, you can try painting on a wall, but for the first times it's better starting with not too wide spaces and with features that might help you in the illusion you are trying to achieve.
The first difficulty that must not be underestimate when doing trompe l'oeil is dimensions: you normally have to handle a drawing quite big, larger than a painting, as wide as a wall or a window...
I suggest you, if it is the first time, to choose a simple subject, do not try immediately a Pharaonic work, with the risk of loosing your spirit in the meanwhile.
Once you have gained your skill with dimension and perspective you'll be able to try more ambitious works.
Let's see now which materials you are supposed to use.
First of all the drawing:
You'd better do a preliminary sketch on a paper and then bring it back on the wall or a big sheet of paper of the same dimensions of the wall, using a division into squares.
The wall must be white painted, and you can paint on it with acrylics, but it's better to give a coat of quartz, or lime paint. The surface must be porous, washable paint do not absorb very well, and do not allow to shade well the colour...
Which colours to use:
There are some kind of colours specifically intended to be mixed together with normal water wall paint, and they are good bases for acrylics, anyway it's better using white quartz paint as base, then once it has dried paint on it with acrylics. (We are not making frescoes, which are supposed to be painted on quicklime)
The best mark is Maimeri because it has a good quality for an enough cheap price.
Once the painting it over you can give a protective coat in order to make the painting waterproof....
I suggest you reading the step by step lesson which explains how to paint a trompe l'oeil.