If not, it is certainly a capital gain if you live in the United States.
And capital gains are taxed. Again if you are in the US and you are not a trader, you will be taxed at a different higher rate if you sold it in less than a 1 year period.
Over a year and it is called a long term gain and the tax rate is lower. There's more about how to write off short term losses and gains, but that's getting into complexity you probably don't need to know about.
