Cyber Monday refers to the beginning of the week just after Thanksgiving. For online retailers, it's one of the busiest shopping days of the holiday season. As online retail business has grown, so has Cyber Monday; in 2010, online sales for Cyber Monday reached the billion-dollar mark.Economic researchers had long known that the Friday after Thanksgiving was an especially busy shopping day, but in analyzing Black Friday trends, they spotted a surge of online sales on the Monday following Black Friday. They theorized that as shoppers who spent the long holiday weekend after Thanksgiving in crowded stores returned to work, these customers still had shopping on their minds. While being at the office once precluded getting the holiday shopping finished, the increasing popularity of online retail shops lets office personnel scratch the last few names off their holiday gift lists. Parents who took children with them to the mall to window-shop on Black Friday could make their purchases online on Cyber Monday without spoiling the surprise for the kids.Cyber Monday originally grew out of Black Friday, the initial hectic day of the official holiday shopping season. Shoppers who chose not to brave the teeming crowds of Black Friday bought online. Office workers who didn't have computers at home raced to their office computers as soon as the long weekend was over. Although most shoppers now have internet access at home or from their mobile phones, the tradition of shopping online on the Monday following Thanksgiving remains thanks to abundant sales and promotions.Cyber Monday has also begun to affect the physical shops that first led to its creation. Brick and mortar retailers, seeing an opportunity to tie their products to that billion-dollar online market, frequently offer Cyber Monday holiday sales on electronics, computer components and games. As with Black Friday, Cyber Monday means extended hours of operation and deep discounts for shoppers at brick and mortar malls.While all online retailers benefit from the surge in traffic on Cyber Monday, stores that sell electronics typically see the greatest upswing in sales. Whether that's because these products lend themselves especially well to online shopping or because the discounts on these items tend to be particularly large then is hard to say, but electronics and appliances are the top choice for Cyber Monday shoppers. Books and electronic readers also sell well on Cyber Monday.