Text messaging and instant messaging are similar. Text messaging, or simply "texting," is a cellular phone service typically limited to 160 characters, whereas instant messaging is usually a computer session with a longer message size.
After a text message is transmitted, the session is essentially ended even though the recipient can respond and keep the back-and-forth going all day. When an instant messaging session is started, it remains connected until the session is ended by one of the parties. Both text messaging and instant messaging are often called just plain "messaging." See text messaging
and instant messaging
Text Messages Can Initiate Things
Another difference is that with texting, users can activate some function by sending a word or two to an organization that has been assigned a coded destination address (see short code