What is a PSN account?
"Starting today, PlayStation Network (PSN) users will gain the ability to upgrade a sub account to a master account, " Lempel wrote. "We’re always listening to user feedback, and this is a feature that many of you have asked for. You’ll be able to upgrade an account first through the web and later through PlayStation 4."
You can find the steps necessary for the upgrade in a new PlayStation Knowledge Center Article. PlayStation 3, PlayStation 4 and PlayStation Vita owners are eligible and will keep their online ID, trophies, friends list, games, videos, music and other services. Both the master account holder and the sub account holder will be notified of the change.
"Upgrading to a master account will allow you access to the full range of online and account features without losing access to your Friends List, Trophies and any Store content purchased on the sub account (even if funded by the master account), " SuperFastZombie wrote.
Sony Network Entertainment sub accounts are designed for players under 18. They are beholden to and must be created in association with master accounts. A parent or guardian holding a master account can monitor the activities in sub accounts, whose holders are limited in several ways covering features like spending limits and gameplay broadcasting restrictions.