SMS stands for "Short Message Service" and it refers to texting in cell phones. If you get a text message from a number you don't recognize, you can use that number to trace it back to its source. Some companies will actually send unsolicited advertising texts out that could cost you money depending on your texting plan, so it's a good idea to identify the source of a number if you get a lot of texts from it and don't recognize it.
Visit the site Trace Text. Enter the number you got the text from in the main textbox on the site. Click "Search Now!" This will give you the number's general location. You'll have to purchase a subscription to trace it back to the exact address.
Download and install the app ReverseLookup for your Android phone. This application lets you look up a phone number that has tested you directly from your android phone and trace where it came from. This version of the app is free to use.
Visit the website Ugux. This site is completely free to use, and allows you enter the number that texted you, area code first, into the three boxes on the site in order to search the online public directory for a trace on the number.