In general a patent contains a number of claims. If a claim references another claim - e.g. claim 2 says something like "A device as in claim 1, where ...." - then clearly those claims must be read together. If a claim does not reference another claim it stands on this own. If you do exactly what the whole of any one claim describes, you are infringing that claim. If you do some of the things in a claim, but not all of them, you are not infringing that claim. You only need to infringe a single claim to infringe the patent. If you try reading the claims in a few patents, this last point should be obvious. Typically the claims are a series of variations on a core theme. You would never infringe more than one or two of them. The list of claims is constructed to ensure each claim is narrow enough in scope to be acceptable to the patent examiner, yet the whole set is broad enough to cover everything the inventor believes they invented.