There is a difference.
Maria and Robert are sitting at the table, eating. There is no salt on the table, but Maria wants some. She asks Robert, to go into the kitchen and bring some salt:
Ger: Robert, kannst du bitte in die Küche gehen, und mir das Salz bringen?
Eng: Robert, please can you go to the kitchen and bring some salt?
Here, in this example you can not use »mitbringen«. Only »bringen« is possible here.
You can use »mitbringen« only if the person, who brings something, was already there where they come from. So they come anyway, and, as a side-effect, they also bring something.
The prefix mit- has always the meaning of co-, i.e. in addition to something else. So it's some kind of "cobringing". The person is comming anyway, and co-brings something. So, bringing is in addition to coming.
If somebody is going to another place for the only purpose to bring something from there, then it is just »bringen«. This person is not coming from there anyway, so bringing is not done in addition to something else. So it's not co-bringing, but just bringing.