Hello Brief refers to time. For example "I was there briefly" - means I was only there for a small amount of time. "I will give you a brief explanation" - means I will not take a long time giving you the explanation. Short really means the opposite of tall. For example "He is short" if he is only 4 feet tall. It can be used more generally to mean small. "I gave a short answer" - means I gave an answer that was not very long. Short can also be used for time. "I will see you in a short amount of time" - means I will see you in a small amount of time. You can also say "I will see you shortly". People use "shortly" to mean "soon" but it is not the same as "briefly" "I will see you briefly" means I will see you for a short amount of time "I will see you shortly" means I will see you soon Hope this helps!

In most contexts there is no difference. 'There was a brief pause' = 'There was a short pause' However, sometimes 'brief' means a shorter length of time than 'short'. 'She gave him a brief glance' is a bit different from 'She gave him a short look'.