The selling points of a variable annuity are that the underlying investments grow tax-deferred, as in an IRA, and that when you retire, the annuity will pay you an income, based on how well the underlying investment performed, for as long as you live. Annuities are sold by insurance companies, and use an insurance policy to provide the tax deferral. It means that taxes are delayed. Unlike a conventional IRA, the money you put into an annuity is not deductible from your taxes. And also unlike an IRA, you may put as much money into an annuity as you wish.
Most people are much better off in an equity index fund.
Index funds are extremely tax efficient and provide, overall, a much more favorable tax situation than an annuity. The growth of an annuity is fully taxable as income, both to you and your heirs. In plain English, the IRS treats the index fund as though your heirs just bought it at the value it had when you died. This is a major tax advantage if you care about leaving your wealth behind. Tax considerations aside, the index fund is a better investment.