A yoga mat for beginners is like all other yoga mats. It is not specialized in any way or unique to one specific branch of yoga, but it is multi purposed to accommodate almost all branches of yoga to some degree or another. If you are uncertain about the style and type of yoga mat you need just keep your eyes open for these particular qualities listed below and you will be able to find a mat that will work for you.
Protection is the number one benefit that you can get from a yoga mat for beginners. You will likely be on a hard surface and having a little padding when you first start out can be really reassuring. If you slip and fall the damage will be significantly less, not to mention the reduced pressure on your joints and limbs as your grow stronger. With time this changes but at the beginning you will find the protection very necessary.
Traction and stability are other qualities that your standard yoga mat will give you. You will see this when you first do a down ward dog. In this upside down V position your hands and feet need to stay put and if they slid out you will find yourself flat on your face. Overtime as you gain strength you find that your own muscles stabilize your poses and give you traction as you go, but at first go a mat can be a huge help in this particular area.
The last benefit that a mat can provide a beginner or any level of yogi is simply a defined practice surface. It is nice to be able to see where you belong and to have guidelines to keep you in the space you need to be. This is really helpful when you first start out and you are gaining a sense of spaciousness all around you. Your mat is a automatic guide line for you as you go.