Recharacterization changes the original contribution to be the opposite type as if the contribution had been the opposite type from the beginning. For example, of the original contribution is a deductible contribution to a traditional IRA and you recharacterize the contribution to be a Roth IRA contribution instead, the contribution is treated as if it was originally contributed to the Roth IRA to begin with and you would get no deduction (since the traditional IRA contribution would be treated as never having been made).
A Roth conversion moves funds from the traditional IRA to the Roth IRA without treating the traditional IRA contribution as never having been made. The federally taxable amount of the conversion is calculated on Form 8606.
