SMS stand for "short message service". It is used to send messages up to 160 characters long to mobile devices, e-mail or voicemail. If you want to send an SMS message on a Mac, you can do so with the iChat software. iChat comes preinstalled on all modern Mac computers and allows Macs to send instant messages to each other from various places. All you need to use iChat to send an SMS message on your Mac is a MobileMe account or an AOL account.
Open iChat on your Mac. iChat is in the dock or in your "Applications" folder.
Log in to your iChat account with your AIM or MobileMe name and password.
Select "Send SMS" from the File menu.
Enter the number of the mobile device you want to send the SMS message to in this format "+ number" with "number" replaced by the actual number.
Type your SMS message into the box. Press "Send."
To send an e-mail SMS type the person's e-mail address proceeded by a "+" in the first field.
Be sure to include the area code of the mobile device to which you are sending the SMS message.