Most of the East Asian follow the lunar calender, according to luna rcalender people celeberate the new years day. Korea is also one of the asian countires who follow strictly into the lunar calender and somehow it falls into the same day of Chinese new year.
I can say the lunar new year of Korea is one of the biggest festival in the country where most of the shops and vendor shut down for at least two days as people go back to their own respective home town to celeberate the new year with their parents as well as family.
In this very auspecious day people wear their traditional dress called Hanbok and prepare mandu and other traditional food items along with their parents and offer to the ancestor first and then share with one another.
On the other hand people like us , I mean the foreigner's we walk around the street but as the street goes so deserted that we find it very strange. Although, a big places like Myongdong and other market some families and couples hangout together holding hands and walk around the street, as a part of celeberation.