What is a psychological intervention, and how does it work? Which ones work best for which kind of issue?

Are there different interventions for different issues, and how and why have they been developed?

What does an intervention look like? And what are the main aims and methods that interventions use?

Do psychological interventions even work? And, if so, who do they work best for?

Are biological interventions still useful as therapeutic interventions? Are such interventions any less (or more) ethical than other types of interventions? Discuss.