There are several types of brokerage accounts, each with different tax treatment. A standard brokerage account is generally taxable, and you'll need to pay taxes on any capital gains, dividends, or interest. Short- and long-term capital gains as well as qualified and unqualified dividends are all taxed differently, and your tax rate will depend on your income level and filing status. When it comes to retirement and education savings accounts (IRAs and 529 plans), those are tax-deferred, which means you are not taxed on earnings in your account, but you could owe taxes when you withdraw the money.
Talk to an advisor about the types of investments that are best for your tax situation and financial goals.