Minecraft shield was first introduced in Minecraft 1.9 and was added in attempt to balance new PVP mechanics. Most of PVP community didn’t really accept this idea tho. Minecraft shields can be obtained by crafting wood and iron ingot, it’s also possible to repair them and to use banners on them.
On most public servers you still won’t see them tho mostly because they’re running Minecraft 1.8 because of performance issues introduced in Minecraft 1.9 and later.
Shields can also be enchanted, but only via anvil, the following enchants are available: Unbreaking, Mending and Curse of Vanishing.