The setting in Claude that decides how thoroughly Claude thinks before it answers.
There are five levels: Low, Medium, High, Extra high and Max. Low and Medium are enough for routine work and save usage; higher levels pay off for hard questions and long tasks and take longer. On the newest models thinking cannot be switched off, so the effort level is the lever. You find it next to the send button when you click the model name.
Example from Basics
In the course's fictional plant shop, Claude copies the ticket numbers into the report template on Low. For the question which open item is overdue, the Customer Care team lead sets High.
Basics: “Claude bedienen”. In the Werkbank course room, with sign-in.