In individual therapy, the “client” is the individual who seeks treatment.
Individual therapy can help people learn to accept things they cannot control, or make decisions about how to take action to control the ones they can. That’s fine for things like illnesses, or career difficulties, or uncertainty about one’s identity.
Individual therapists have traditionally seen clients once a week for 45-60 minutes. This provides some stability for the client, and creates a place where the client regularly pauses in life to reflect, evaluate their progress toward their goals, and make decisions. In some ways, it is like the weekly review that productivity gurus tell us we should have, every week, to assess our work but also personal life goals and our progress toward them.
For individual therapy, there are many studies that show the effectiveness of many different models. Sometimes they show one kind of therapy is better than another for a specific problem, but more often not. More often they show most therapies can help with most all problems.