A list's visibility and accessibility are settings you can edit yourself, for example whether a list should be public or not. This guides guides you through the process and elaborates how it is done in the system.
This guides elaborates how you create lists and data fields. Lists can be used for segmentation and data fields can be used to collect information about you subscribers. This information can then be used for segmentation. The guide also elaborates how you can import and create a sign up formula on your website.