This term refers to the Japanese tradition of giving gifts during summer as an expression of gratitude. These gifts are typically given to show appreciation to people who have helped or supported you.
Related terms
お歳暮 (oseibo): Similar to お中元, but it refers to the year-end gift-giving tradition.
ギフト (gifuto): Refers to gifts in general, regardless of the occasion.
感謝の気持ち (kansha no kimochi): The feeling of gratitude and appreciation.