Anger is not as well studied and understood as anxiety. While anxiety conditions have names like GAD, OCD, etc. the only references to anger are in extreme cases like antisocial behaviour or oppositional defiant disorder, which probably not many people know about.
Anger is an emotion that we all experience in life and, unfortunately, is not easy to express. Anger can become chronic and unhealthy, which is when clients start considering the idea of coming to therapy to make sense of it. Typical scenarios are
Getting very irritated at small things
Raising voice in work situations
Losing trust in people
Hitting (or wanting to hit) parts of one's own body or other objects
Getting easily into arguments that escalate quickly
The field of CBT has worked mainly on the idea "anger management" to help people contain their anger and express their point of view with assertiveness. In addition to this, there is a need for understanding the causes of one's own anger and all the other emotions that go with it.
Here are some of my articles on anger