VIP memberships are a way to pay in real world money for more cards. There are 3 levels of Plan offered, and many Tiers: renewing a membership increases VIP Tier, leading to bonuses.
VIP Plans and Tiers
VIP memberships were introduced in May 2019 and pitched as a way for players to "achieve better rewards faster through game progression without detracting from the fun and engaging experience of the game". A FAQ is available with this announcement, found here
Pro Tier is good value for the money, at the cost of acquiring cards more slowly. Pro and Master Tiers are identical, for the price, when it comes to boosters, where Master simply gives twice as much for twice as much cost. The same goes for Crystals. But Pro provides two Legacy rares, and Master only one: three short of the double amount it should give for its price. Neither does it provide double the Standard rares, but only equal; or 50% more, if a card from the newest set is considered equivalent to a Standard one. The extra Mana Jewels Master provides are negligible; insufficient to buy more than a single Rare from Elite packs. The real draw for Master is its Legacy Mythic Booster, making it, and not Pro as common wisdom has it, the more effective at acquiring a full Legacy collection.
A common strategy is to not open Legacy Booster Packs until all Commons and Uncommons and Rares are acquired, by free packs and Booster Crafting and VIP plans. The packs are forced, since they are non-duplicate, to be filled with only Mythics and Masterpieces.