Indicates that something has been understood, acknowledged, or accepted; often used in business or conversation to mean confirmed/approved.
その件は上司に確認してあり、了解済みです。
I have confirmed that matter with my boss; it is understood/approved.
メールでの依頼はすでに了解済みなので、作業を始めてください。
The request in the email is already acknowledged, so please start the work.
参加者全員から了解済みの返事をもらった。
I received confirmations from all participants.