From English 'easy'. Means simple or not difficult; often used colloquially as a na-adjective.
この問題はイージーだから、まずはここから解こう。
This problem is easy, so let's start with it.
ゲームのイージーモードで操作に慣れた。
I got used to the controls in the game's easy mode.
彼はイージーに成功したわけではなく、努力した結果だ。
He didn't succeed easily; it was the result of effort.