A more thorough explanation:

The doctrine of claim differentiation is a principle used in patent law that assumes each claim in a patent has a different meaning and scope from all other claims. This means that different terms used in separate claims must have different meanings, or else one of the claims would be redundant.

For example, if a patent has two claims, one claiming a "red car" and the other claiming a "vehicle with four wheels," the doctrine of claim differentiation would assume that the two claims have different meanings. If they were interpreted to mean the same thing, then one of the claims would be unnecessary.

The doctrine of claim differentiation cannot be used by the patent holder to broaden their claims. Courts will only apply the doctrine when they are convinced that their interpretation of the claims is correct. The presumption is strongest when a different interpretation would be the only way to make a dependent claim more limiting than the independent claim it refers to.

Overall, the doctrine of claim differentiation helps ensure that each claim in a patent is distinct and has a unique meaning, which helps prevent confusion and redundancy in patent law.