Here's a brief explanation of short-term vs. long-term Capital Gains.
Short-term designation: A short-term gain occurs when a Capital Asset (in this case your Cryptocurrency) is bought and then sold or exchanged within one calendar year.
Short-term tax: Short-term capital gains are subject to the taxpayer's marginal tax rate. That is the rate the taxpayer pays for each additional dollar of income earned and includes Federal, State, and Local Income Taxes. These rates can range anywhere from 0% to over 50% depending on where you live and how much you earn.
Long-term designation: A long-term gain occurs when a Capital Asset (in this case your Cryptocurrency) is bought and then sold or exchanged after one calendar year. For example, you bough Bitcoin in January 1, 2012 (you're a genius) and you sell that coin on January 1, 2013. This would trigger a long-term gain.
Long-term tax: Long-term capital gains are subject to the taxpayer's long-term capital gains rate. For taxpayers in the 0% or 10% Federal Tax brackets, their Federal long-term rate is 0%, for taxpayers in the 15% to 35% tax Federal Tax brackets their Federal rate would be 15%, for the people in the highest Federal bracket (39.6%) their Federal long-term rate is 20%. On top of the Federal rates of 0%, 15%, and 20%, their are also State and Local long-term capital gains taxes. For example, in New York your long-term rate can be as high as 31.5% (20% + 11.5% New York state rate), and in California it's even worse with rates on long-term gains going as high as 33%!