The lens is probably the most important piece of gear any photographer will carry, having a tremendous impact on the technical and creative qualities of your images. If you are new to photography and wondering what you need to know about lenses, check out this fantastic video tutorial by an Australian Geographic photographer that will teach both their standard properties and the fundamentals of their usage.
Coming to you from Chris Bray Photography, the excellent video tutorial will show you everything you need to know about lenses. Most entry-level cameras come with a kit lens, but generally, these lenses have severe limitations, including poor image quality, slow focusing speeds, and narrow maximum apertures. Grabbing an affordable, wide-aperture 50mm lens (commonly known as a "nifty fifty") will teach you quite a bit more by allowing you to experiment with wide apertures and the corresponding narrow depth of field, work in low light, learn the advantages and disadvantages of a prime lens, and more. Once you get a feel for that lens, you will have a much better sense of what you are looking for before you start investing serious money in glass. Check out the video above for the full rundown from Bray.
what you need to know about lenses is simple
don't start with more than one lens for the first year - and preferably a short prime
don't get another lens until you can picture the photos you would have taken if you had it.