Hi Maria the pretty, in China the Spring Festival 春节 refers to the first day ( or a few days , 5 or 10 or 15) of a new year of traditional Chinese calender ( a kind of lunisolar calender 阴阳历).
Historically 春节 had been the same as the solar term 立春( time when farmers begin to sow for the new year, on Feb. 4 or 5 in Gregorian calendar); and this is where the name for 春节 come.
But later it was transfered to the boundary and joint between the old year and the new year, because Chinese people believe the beginning of a year(and everything else) is more important and symbolic.
In today's calender of China, 春节is on the first day of January of the traditional Chinese canlender, and this day is called 大年初一. Certainly it is big day in the Spring Festival, but more important is the eve of this day 大年三十 ( the 30th day of the last month of a year), because in Chinese tradition a family will come back home from everywhere to reunite, and most Chinese people today faithfully observe this custom. In the following a few days people will visit ralatives and friends, hold parties, and take part in all kinds of festivals and revelries.
春节is very literal and formal. A more common term people will say to call the traditional new year (days) is 过年, 年. People will greet each other with 过年好,新年好,给您拜年了 and so on when they meet. And they will write to each other saying 恭贺新春, 恭贺新禧,祝您在新的一年里万事如意, and so on.
In public affairs, China takes the Gregorian calender, while as folk festival, the Gregorian new year (day) is much much less important than the traditional one, although there will be many commercial and entertaining and other events taking place during the period.
In the Gregorian new year (days), people will say 新年好(happy new year) to each other, and write to each other saying 新年快乐, 祝您在新的一年里万事如意 and so on.