I'll define it by century:
19th - Honest hearted Bible Students who were a special people chosen by God as the final part of the 'remnant' annointed. Sharing God's plan with mankind was the mission. A non-religion who met informally in small groups and used Russell's writings as a study aid. The end of the world was coming in 1914.
20th - God has a chosen "earthly organization" who's mission is to spread the good news of Christ's enthronement to the world. The message is geared toward increasing the organization's population by active proselytizing - to bring 'honest hearted / sheeplike people' into the the 'great crowd' or "the Truth". Families would soon be entering into the "New Order" hand in hand to welcome back their resurected relatives and friends.
21st - The leadership of the central organization takes complete control of the membership. Matters of individual conscience and personal decision making cease to exist. Jehovah's Witnesses are now a religion - with a hierarchy (laity and clergy), the confessional and penance. The leadership is no longer a faceless group. Obeying the organizational structure and rules override scriptural principles.
ginger