A membership website is a set of pages with protected content that require a user to login to access. A membership site will often house content that is available to only those individuals who have paid a membership fee. This membership fee could be a one-time fee for lifetime access or a recurring subscription that charges a set dollar amount each month or year.
Membership sites are not just for products, though. Many online communities and similar kinds of projects use membership features to isolate the kinds of people that are only in it for the thrill of it. Community forums might want to utilize membership features because that would keep a set of professionals within a tightly sealed circle that would require a monthly payment to be a part of, which in turn creates a kind of atmosphere where more high-quality discussions and content sharing is encouraged.
A checklist is a type of job aid used to reduce failure by compensating for potential limits of human memory and attention. It helps to ensure consistency and completeness in carrying out a task. A basic example is the "to do list". A more advanced checklist would be a schedule, which lays out tasks to be done according to time of day or other factors. A primary task in checklist is documentation of the task and auditing against the documentation.