When you sell shares from your IRA, you won't owe income taxes or capital gains taxes on investment gains, as long as they remain in the account. Since earnings are not taxable, you won't be required to include them as income when you file your annual tax return. On the other side of the coin are tax losses. When you sell stocks at a loss in a taxable account, you can deduct losses from your profits and even from your regular income up to a limit.
If you sell a stock within an IRA at a loss, you won't get that benefit.