The giving of Red Envelopes is a quintessential part of any Lunar New Year celebration. They are also known as ang-pow in Hokkien, lai-see in Cantonese, hung-bao in Mandarin.
Red envelopes are given as gifts to children and single adults during Lunar New Year and weddings. Inside each envelope is usually some gold coins or crisp dollar notes...the amount depends on how generous the giver is. The tradition of giving red envelopes dates back to the Sung Dynasty. Growing up, this was one of our favorite celebrations because we all got money even from long lost relatives and friends. 
Here are the typical gift giving scenarios -1. From parents to their children
2. From married adults to unmarried children in the family (uncle to nieces etc)
3. Adult children to their parents
4. When visiting family and friends
5. From employers to employees
Limited quantities in store now. Lunar New Year starts on 22 January.