On one day every year, we officially celebrate the mothers in our lives: the women who care for us, support us, believe in us and probably don’t get all that much credit for everything they do.

讲解
大意：在每年的这一天，我们会比较正式地为母亲庆祝节日。妈妈，她关心，支持，信任我们，同时不求回报地为我们付出。
officially：正式地
celebrate：庆祝
get credit for sth/doing sth：把某事的功劳归功于自己