I could not find a better answer to express the red envolope meaning behind Chinese culture.
Actually, you can understand "抢红包" like this: many people are scrambling a gift happily.
FYI: usually "red envelope" means a small package with money :)
订阅开奖提醒: you can understand it like this: subscribe it and it will send a notice to you when will begin to 抢红包.
I did a little research and found this on "Chinese wikipedia", and translated it for you:
Giving out 红包 is a Chinese convention during New year (Festival). In China the color red stands for joy, luck and happiness.
Giving out 红包 to someone (usually 18-) means bringing luck and wish to them. And the money in it is only to make kids happy.
Below is the original article: