to treat (someone) to (something); to give (someone) a treat; to buy (someone a meal, drink, etc.)
to be extravagant; to live in luxury
今日の夕飯は俺が奢るよ。
I'll treat you to dinner today.
先輩に奢ってもらった。
My senior got me a meal.
昇進祝いに後輩全員に焼肉を奢った。
To celebrate my promotion, I treated all my juniors to yakiniku.