A patent’s front page contains information such as the patent number, the names of inventors, the name of owners, date of priority (from which the legal rights start), and usually contains an abstract, summarising the invention.
The main body of a patent contains figures and their explanations, which pictorially describe key elements of the invention and data proving its efficacy, a section describing the background to the invention (what problem is being resolved, what other unsatisfactory solutions may already exist, and why it is important to find a better solution), followed by a summary of the invention (in greater detail than in the abstract).
A detailed description of the invention then follows, and typically includes a detailed description of experiments that demonstrate how to make the invention work. Finally a number of so-called claims are listed.
The part of a patent that is most important and provides legal and commercial protection is the claims of the invention. A patent application typically contains a series of claims, which describe in detail what the invention is, how it works, its scope and limits. This can be composition-of-matters claims, methods for making things, the specific use of a material to achieve certain functions, series of steps to be undertaken to provide a certain outcome, a new use for a known compound or entity, an algorithm that transforms input data into useful information, etc..
An invention is covered by a patent only if it used in the way that is described in the claims, or made of at least the composition described in the claims, or made according to the method described in the claims.
Drafting appropriate claims is a skill, better left to patent attorneys.