MT stands for Mobile Terminated.
MO stands for Mobile Originated.
MO is basically when your customers sends the message from their mobile phone to your system.
MT is basically when your system sends out the response to the text which it receives from your customer to their mobile phone.
This transaction basically used in 2 Way SMS Marketing.
For Example: Customer sends a text to Pizza to a shortcode 55555 is called Mobile Originated. And system sends the response message to the customer who sent Pizza as text saying “Thank you for joining our group” using bulk SMS application is called Mobile Terminated.