text messaging vs. instant messaging - Computer Definition
Both systems are similar and increasingly add features that make texting and instant messaging resemble each other. However, the primary difference is that text messaging is a cellular phone service that is 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. See text messaging and instant messaging.