Way back in 2003 Apple and AOL partnered up allowing AOL users to log into iTunes, the App Store and iBooks Store with their AOL credentials.
Apple has recently emailed users to advise that starting on Tuesday, March 31, Apple will no longer allow log-ins to with those AOL credentials.
Apple has posted a support document on their site stating that users simply need to sign into to iTunes with a Mac or PC and then follow the on-screen instructions to convert their account into an Apple ID.
If the AOL information isn’t converted by that date then users means you will lose access to the stores and any content that had been previously purchased and Apple will be unable to provide any assistance
The change doesn’t affect any access to AOL-specific services using your AOL credentials.