High-income individuals and their spouses aren't permitted to contribute money directly to a Roth IRA. But there's a way around the Roth income limits for people who'd like to avoid taxation in retirement, known as the backdoor method. Here's a rundown of why this may be necessary, and how the process works.
With a traditional IRA, your ability to deduct your contributions is limited only by your income if you or your spouse are eligible to participate in a retirement plan at work. And even if this is the case, you can still make nondeductible contributions that can grow tax-deferred.
Source: Fool.com