The red envelope ( 红包) Hóngbāo custom is all about the reciprocity of giving and receiving and the money inside Hóngbāo is called 压岁钱 Yāsuì qián.
The character 岁 suì is another Chinese character for 'year'. It has the same sound as 祟 suì, which stands for 'evil spirit' in Chinese culture. So the Chinese expression 压岁(祟) 钱 Yāsuì qián, which describes the money in the red envelope, is a symbol of the wish to suppress/expel all the bad in the coming new year.
It’s a gesture of goodwill, expressed through the exchange of red envelopes, that builds relationships among family and friends. In fact, after all the giving and receiving of red envelopes during Chinese New Year, you’ll probably find that you end up netting even financially. Count the relationships, not RMB!