I consider this to be a general question. Please feel free to move it.
When Trump gives a speech, the sign on the podium says, “TEXT TRUMP TO (some 5-digit number)”. So what happens if I do that? What happens if I misspell “FRUMP” or even “KISS MY ***”. And lastly, how can I get a 5-digit text number?
Of course we can. Watch and be amazed how I do just that.
If you do it, you get put on a list to get regular updates, via text, about the campaign. If you text something other than the key word (in this case TRUMP) nothing will happen. They might have different key words for different things. Maybe you could also text DONATE or VOLUNTEER to get different information.
ETA: another would be to text STOP to not get updates anymore.
I forgot to answer the second part of the question. Those things are called SMS Short Codes. Below is a link to an article from a company that sells them. It does a pretty good job describing how they work.