To become a member of the LDS church, sometimes called "Mormon", you must be baptized and confirmed by duly appointed representatives of that church. In specific, the people who baptize and confirm you must hold the appropriate priesthoods. Before you can be baptized, you must undergo a "baptismal interview". Among other things, the interview will most likely ask you if you (a) have read the Book of Mormon, (b) believe that it is true, (c) have attended church services, (d) have faith in Christ, (e) have repented of your sins, and (f) agree to abide by some specific commandments, namely the Word of Wisdom (abstaining from alcohol, coffee, tea, and tobacco), the Law of Chastity (abstaining from sexual relations except within the bonds of marriage), and the Law of Tithing (that you will donate 10% of your income to the church). Normally, one would undergo a series (6) of discussions with the full-time missionaries prior to this, so it's not like the interview questions would be totally out of the blue.