According to JW dogma, they believe God has continuously had "an organization", even during the Dark Ages. Until the death of Jesus, it was the Jews. Then, until 1919 it was the churches. Now, it's JWs. Of course, this is utter crap, just like the Catholic Church's claim to be able to trace Popes all the way back to Peter. Similarly, if you ask a Catholic about it, they'll become indignant and insists they can, but Catholics are the only ones who believe it, just like JWs are the only ones who believe in the whole "organization" thing.
It's just a way to enforce their idea of what the "faithful and discreet slave" of Mat 24 means. They teach there was a "governing body" in the 1st Century and this is crap, too. They teach the "faithful and discreet slave" was chosen by Jesus in 1919 and were put in charge of Christianity; wrong on both counts.
Study doctrine with JWs but don't get caught up in their worship of the printing company, the Governing Body, or "the organization"; it's all idolatry. Do all things to the glory of God and not men or a man-made group or company. They'll start guilt-tripping you with "Who taught you the Truth tm ?" and expect you to understand they are your masters. Simply respond "God", because His Word is the source and the JWs are just messengers; "good-for-nothing slaves" (Luke 17:10) and not gods, lords, leaders, or objects to be worshiped or obeyed.
Be careful when studying with JWs, because that's where their "Bible" study leads. Many things in their books are very biased toward the unbeliever eventually worshiping the Governing Body, the Watchtower Bible and Tract Society, and the Jehovah's Witnesses group as a whole. Keep an eye out for this and don't let it fool you. It is God alone you must worship (Mat 4:10).