This convention is built in, in the conventional 2-level minor suit openings.

The purpose is to enable the opener to show 3-suited hands in order to find a fit. (hence the name: wie-van-de-drie = pron. weevandedree + transl. which-one-of-the-three (..... will be the trump suit?). There is a popular TV-game, in which people try to guess through putting questions the right one out of three persons, e.g. in order to remain in card terms: the real queen out of three ladies who all claim to be queens while only one is. In Holland this game is also called: wie-van-de-drie. When I'am not doing something on bridge, it's very likely that I am watching this fascinating game on tv.
Since three suited hands are not encountered often, the primary attention of the bidding system is paid to more often occurring distributions.
As a consequence of this, the bidding level on which a three suited hands are shown is quite high. This is no problem because such hands, if bid through the 2-level minor suit openings are always very strong. Moreover with one bid it is possible to reveal the hand completely.

With three suited hands and opening hcp's, you may always consider a 1 or a 1 opening, and if you are strong (16-19) you can rebid with a SHiD+++ or MaD+++ call to show your strength and distribution. Having to open with 1 in a major suit is also imaginable with some hands (5,4,4,0); this also should be considered in relevant cases.
On the other hand, if you think you are very strong, you may choose for an opening bid of "two" in one of the minors.
This ends up in the conventional, hand describing, 'WEEVANDEDREE'-rebid:

If you did not guess it already, the reason for the strange name of the convention must be clear by now: Which one of the three suits, other than the suit the rebid, is going to be the trump suit? This is a question to which the responder must reply. He also must decide about applying Blackwood and establish the level of the final contract.
The 2-level minor suit openings commonly do not require jump responses and jump rebids. Therefore it is possible to use a jump rebid to point to the strong three suited hand of the opener.
We could agree to use the "Jump Rebid" (or "J.R." which makes me remember that unforgettable tv program that always came after 'wievandedrie ') for this, and allowed for one exception on this jumping rule with a weak responding hand after a 2 opening bid, where 3©/ never point to weak 6-suiters. With weak 6-suiters the bidding never exceeds on the 2-level, unless the responder is strong.
After a 2 rebid there is a problem because the meaning of any rebid in hearts is always real. Having a void in hearts you cannot do anything else but call 2NT (or 3 in a minor if you possess a 5-suiter). With a 6-suiter spades you must pass (stay on 2-level).
A 2 responder must be conscious of the two way character of the 2NT rebid, and should try to call a 4-suiter on 3-level.
You may also choose to get around all these problems and apply the 4©/ in all situations, so also when the responder is weak. However the odds are 5 to 6 that you end up in a 5-level contract, which may be just one level to high. I have no experience for that matter, because I never encountered the situation.

The "weevandedree" (or if you prefer J.R.) "convention is maf like usual, but she does seem to hard to memorize, once you know that the three suited hands are also covered by the multi-way minor suit 2-level openings.

If you still have problems memorizing the convention, like I have, you should use next reconstruction tip. Some rebids are booked by strong major suit hands. We knew that already. We also knew, which opening bids belong to what suits. We may conclude from this, which rebids are free. So summarizing:After each of these 2-level opening bids, a number of suit rebids has been reserved, and we know which ones. The remaining suit rebids are allocated to the singletons

If you want to see examples of bridgames, in which the matter, treated above, is practiced, you should click on examples and choose for the appropriate convention or for any other typical call.

This convention is part of the MeRDe-complex ("MeRDe "= "Mean Repulsive Devices ", 'merde ' also is the french translation of 'shit '; it is used quite often by angry Frenchmen).
This complex consists of the next, void or singleton showing, conventions: SHiD+, SHiD+++, splinter, MaD+++, CUE, WievandeDrie and SHiCe