You can share lists or folders with people by adding them as a member to that list or folder.

To do so, open your list or folder settings, click/tap "Access" and choose "Add Member".
You will then be able to type in the name or email of the user your want to add.

It's not possible to share lists and folders, or individual tasks, with non-members. If you want to share a list, we suggest you use the email or print functions to send it to them.