A keyword is a unique word (or number) that is created for a specific short code SMS campaign. Multiple keywords can be used on a single short code active during a single period. The keyword is the actual text that a user keys in on their mobile phone to interact with a campaign. Keyword as a word or name used to distinguish a targeted message within a short code service is very useful for some reasons. Some platforms allow marketers to distribute a keyword for users to subscribe to text messages, due to reasons that text messaging is so intrusive, most providers require opt-in approach. That is, you text the keyword to the short code, then you get a request back asking you to opt in with a notice that the messages could incur charges depending on your provider. The subscription platforms typically allow you to schedule text messages and view reporting on campaign effectiveness.