Peat has been extensively used for years as a soil amendment or an ingredient in the mix for potting composts. Nutrient level is low to non existent, but because it holds onto water, it can also retain nutrients which are present in the potting mix or garden soil. It has an acid ph, and there's usually a high proportion of peat in potting mixes for acid loving plants such as Camellia or Rhododendron.
Peat, though, has taken millennia to form - it is not a renewable resource, and carbon is released into the earth's atmosphere as peat is removed from the bogs where it is found. Peat use is restricted, controlled or banned in many parts of the world for these reasons, and many gardeners avoid any product which contains peat because of these ecological principles. Primary use these days is by commercial growers, so if you are still able to buy it, use it sparingly. If you were thinking of using it as a soil amendment, composted materials are more beneficial anyway, adding humus to the soil and improving soil bio diversity, so things like composted animal manures, leaf mould, your own compost from your heap or bin are better choices. More info here: Peat Moss And Gardening – Information About Sphagnum Peat Moss.