(CBS) – Today is “Green Monday,” one of the biggest online shopping days of the year. Experts project consumers will spend $1 billion on holiday shopping this day alone. And today is also the busiest day for shippers nationwide.

But what exactly is “Green Monday”?

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“Early Show” Consumer Correspondent Susan Koeppen, reporting live from a FedEx facility in Brooklyn, said, ” ‘Green Monday’ is an online retail industry term similar to ‘Cyber Monday.’ The term was coined by eBay to describe its best sales day in December, traditionally the second Monday of December. “Green Monday” is defined more specifically by business research organization comScore as the Monday with at least 10 days prior to Christmas. In 2009, $854 Million was spent online in the U.S. on “‘Green Monday.” ‘

“It’s basically the trigger day,” Koeppen said. “(It’s) the day that most shoppers realize, ‘You know what? I’d better do my Christmas shopping today to make sure that those packages get there on time for Christmas.” ‘

It’s a big day for shippers, too.

“FedEx says that this is the busiest shipping day for them,” Koeppen said. “As you can imagine, a monster day for retailers. It is a monster day for shippers, as well. Put it into perspective: FedEx says it will handle 16 million packages today alone. That’s a 12 percent increase over last year.”

While this Friday is also going to be Free Shipping Day, not all retailers will be participating.

“This is something that started a few years ago. Every December 17th is now called Free Shipping Day. There are about a thousand retailers that are taking part this year. You can go to FreeShippingDay.com to find a list of those retailers, but if you’re going to use free shipping day, read the fine print,” suggested Koeppen. “. Sometimes there’s something in place like you have to spend $75 or more to get free shipping. So it doesn’t necessarily mean that you buy a $2 item you get free shipping for it. Read the fine print.”

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Another recommended website is CyberMonday.com, which also maintains a free shipping section with a list of retailers still offering the popular promotions for delivery by Christmas.

And there are some deadlines about shipping you want to keep in mind, as well.

“Two-thirds of retailers saying that standard shipping will expire on or before December 18. So that is Saturday. So you have until Saturday, in most cases, to qualify for that standard shipping. But all is not lost if you don’t get the packages out by Saturday. You can still do express shipping, priority shipping. You are going to pay more, but even up until December 23, some places are saying you can buy on the 23rd and still get it in time for Christmas, but you’re gonna pay for it.”

But what should you keep in mind when you choose how to ship your packages?

Experts recommend buying extra insurance for your package if your package costs more than, for instance, the $100 covered by the Post Office.

FedEx highly recommends insuring high-value packages and it offers that service for customers. Also, a good tip is to be extra safe by putting an index card inside the box with your address and the recipients address.

The shipping tips below are also recommended:

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• Use sturdy boxes, don’t use an old box.
• Make sure your contents are in the center of the box.
• Use packing tape, not duct tape.
• And label the address clearly in the center of the box, so it’s visible.