Minecraft wiki entry for Before_Village_%26_Pillage, associated text: Different lists of trades were available.
The trading interface was very different.
Villagers unlocked new trade tiers when they make a trade they have never made before, rather than based on experience.
Not all careers had 5 tiers.
Tiers were not displayed in the trading GUI nor on their textures.
Villagers resupplied trades randomly when other trades were made, and they did not have workstations.
Careers were fixed and were assigned when a villager spawned.
Not every career had a unique texture.‌[Java Edition only]
Trade prices were determined when the trade was unlocked, and did not change.
Villagers did not display items available for trade in their hands.
Villagers lost their trades when becoming a Zombie Villager.
Wandering Traders, Masons‌[Java Edition only] and Unemployed Villagers were not yet added.