A short code is a memorable number between 3 and 7 digits in length. They are ideal for marketing campaigns and promotions where you want people easily to remember your number. Short codes are country specific and can't be used if you want to receive messages from international customers. Therefore you need to have a short code in the country where your customers are.
Long numbers, like the name implies, are long telephone numbers which can be up to 16 digits in length but are usually the length of a standard telephone number. Long numbers are cheaper to use than short codes and allow you to receive replies from local and selected international destinations. If you need to receive replies to your messages but it’s not as important that people easily remember your number, then a long number is the most cost-effective solution.
Watch this video for a simple explanation of the difference between short codes and long numbers. Please note that specific country restrictions apply to the use of long numbers and short codes in the USA.