Refers to the New Year (the beginning of the year). Used in greetings like 'Happy New Year' and can be used adverbially to mean 'at the New Year.'
新年あけましておめでとうございます。
Happy New Year.
新年には親戚の家を訪ねる習慣がある。
There is a custom of visiting relatives at New Year.
新年の抱負を紙に書いた。
I wrote down my New Year's resolutions.