SMS is a text message plain and simple usually limited to 180 characters.
For example -

Code:

The dog is black

Would be 16 characters.

Now for those of you wondering how to send text messages on a massive scale, don't waste your money on tools saying "SEND TEXT MESSAGES MAKE BANK!"

Want to know how to send text messages? Well here's how.
You can use your favorite email script or client, or however you chose to send emails.

90% of cell phone companies have a "sms gateway"
List -
http://en.wikipedia.org/wiki/List_of_SMS_gateways

Now, you put the area code, prefix #, suffix # @ gateway.tld

For example, if you have a AT&T cell phone number, it would be
1234567890@txt.att.net
broken down -
123 = area code
456 = prefix #
7890 = suffix #
@txt.att.net = @ gateway.tld

Then from there you could put a subject or not, up to you. but the message must be <=180 characters(that includes your link)

Now you must be wondering "okay i have the numbers, how do i find the carrier out?" well here you go -

Code:

http://www.smsmatrix.com/

SMS Matrix.

You can create a free account and you can have I believe 5 or 15 free look ups, Don't remember which.

You can also do this - buy bulk emails(yahoo,gmail,hotmail,etc.)
create the "free account" they offer and use the free account to get the carrier then from there goto the gateway list and grab the gateway "email" and send it out and watch the money flow in.