The main difference between instant messaging and texting is that instant messaging doesn’t rely on the cellular phone service provided by the carrier to send messages.
Texting is possible on any mobile device, regardless of the cellular carrier, and no additional downloading is necessary. On the other hand, instant messaging requires the sender and receiver to download and use the same app to communicate.
Additionally, instant messenger allows sending multimedia content, such as images and videos, along with the text.
Another difference is related to international capabilities. While your international carrier plan determines the locations you can send texts and the cost involved, instant messaging apps make it possible for people to communicate regardless of their geographical location.