In a nutshell, a ROTH Conversion is an IRS-approved process whereby you move assets from a tax-deferred Traditional IRA account to a separate, tax-free ROTH IRA account.
The IRS still requires that taxes be paid during the conversion process, but once the assets are deposited in the ROTH account, they grow tax-free, and your qualified withdrawals can be tax-free as well. That's why ROTH Conversion has become such a popular topic in recent years...