盒子 (hézi) is a noun meaning "box" or "case." It refers to a small container, typically with a lid, used for holding or storing items. The suffix 子 makes it a common, everyday word for various small boxes.
她把礼物放进了一个小盒子里。
Tā bǎ lǐwù fàng jìn le yī gè xiǎo hézi lǐ.
She put the gift into a small box.
桌上有一个红色的盒子,你看到了吗?
Zhuō shàng yǒu yī gè hóngsè de hézi, nǐ kàn dào le ma?
There's a red box on the table; did you see it?
我需要一个盒子来装这些旧照片。
Wǒ xūyào yī gè hézi lái zhuāng zhèxiē jiù zhàopiàn.
I need a box to store these old photos.