You likely hope the investments you hold will rise in value. Still, you have to be aware of how increases in the value of your investments can trigger a tax bill when you sell the investment. Capital gains are generally the profits you realize when you sell an investment that is a capital asset for more than you paid for it, whereas capital losses are generally the losses you realize when you sell an investment that is a capital asset for less than you paid for it.
When you have a capital gain, you may have to pay tax on the gain at capital gains tax rates. Which tax rate applies depends in part on how long you held the asset. Generally, if you hold a capital asset for more than a year, gains on that asset are eligible for long-term capital gains rates, while gains on investments you sold in a year or less are considered short-term. Generally, the tax rate is higher on short-term capital gains.
There are moves you can make to help reduce or mitigate the amount of taxes you will pay on your capital gains, including holding assets longer and tax-loss harvesting. You can also choose investments that may have a tax-favorable profile.