What is a concentration?
An area of emphasis in a program of study; used in the same way as “focus.”
For example, in an English major, a student may focus on medieval literature, or the American novel, or the short story.
In many cases, this would not be official, it would just show in the student’s choice of classes. In some cases, a concentration might be an official part of a student’s academic record and might be listed on a transcript.