Acrylic paints are a recent invention, and differ greatly from the other two main types of paint, oils and watercolor. They are good for the impatient artist, as they dry quickly. They also are very crisp and vibrant in appearance. For those who are used to painting with oils, it is important to know that acrylics dry much faster, and that they can be used without adding anything to the paint.
For those who are used to watercolors, it is important to know that acrylics are much thicker, and are permanent once they dry. For the complete beginner, acrylics are the perfect medium. They are very forgiving, and once dry, any mistakes can easily be painted over top of. Additionally, average quality acrylics tend to come at a reasonable price, as do the brushes that can be used with them.
To start painting with acrylics, a few basic materials are needed. The regular painting equipment is required of course- brushes, a palette, canvas, a water cup, and a palette knife. For those limited on money, a paper plate and plastic knife can be substituted for the palette and palette knife. Any cup can be used to hold water, as acrylic paints are generally nontoxic. I typically keep one cup that is designated as my paint cup.
There are many different types of brushes that you can buy, and all the different names, shapes, and sizes can be quite confusing when you go to buy your first brushes. I personally use large filberts (a flat brush with rounded edges), and small rounds (long bristles in a cylindric shape). Filberts allow you to cover a large area without showing the edges of the brush stroke, like a flat brush (which lacks the rounded edges) would. Rounds have longer bristles, and allow for control over the brush strokes and more detail.
As far as canvas goes, there are three main choices. Regular canvases are pieces of canvas that have been stretched tight over a wooden frame. They are likely the most commonly used, and are, in my opinion, the most professional looking as a finished work. However, if the canvas wasn't stretched tight enough, sometimes it will give a little when you paint, which can be frustrating. Next, there are canvas panels, which is canvas stretched over a hard backing. These don't have the risk of the canvas giving, and are much easier to deal with. They are also cheaper.
Lastly, there are plain canvas sheets, where the canvas isn't stretched over anything. These are easy to deal with as well, and are very cheap. However, they look much less professional, and can't be hung on a wall by themselves, unlike the other two canvas types. I personally prefer regular canvases and canvas panels, and I use one or the other depending on my budget at the time and how I feel the finished piece will look best. In addition to the regular equipment, you also will need acrylic paints. The paints that I have used typically have come in tubes, much like toothpaste, but some acrylic paint comes in jars or bottles. I recommend buying a larger tube of white paint, as in my experience, it tends to run out quite quickly.
Hopefully you find acrylic painting to be as wonderful an experience as I have. It is an enjoyable hobby and for some, has become an amazing career as well.