It is a common practice nowadays to be asked for a SMS number while registering to a site. Most of us do not want to share our phone number on the net to avoid being spammed, making it impossible to complete a registration process.
Luckily there are several free online services, offering the possibility of receiving and reading SMS with one of their many phone numbers. This particular site offers 6-8 numbers which are periodically renewed, free of charge and without any registration needed.
This is great to test applications that charges for each SMS received or to keep to ourselves our real phone number.