In Minecraft villagers gain jobs by visiting an unclaimed job site block, and a lectern is one of the possible options. The lectern creates a job as Librarian for a villager, who emits green particles when they claim the lectern as their own. The lectern also holds books for players to read.
Lecterns spawn naturally in village libraries, sometimes spawning up to 2 lecterns in one library. Lecterns can also be crafted by players.
To craft a lectern players will need wood slabs and a bookshelf. Bookshelves can be found in most libraries and some houses, or can be crafted using any wood and books. Books are crafted using paper and leather, or are found in libraries within most villages.
Related: Minecraft: How to Get Mending Books
Lecterns can be used in multiplayer mode as a stand to hold books all players need to read. A single written book can be placed on the lectern, or a book and a quill for writing books. Players cannot place regular books that are used for crafting, or enchanted books on the lectern, if they do nothing will happen. Only written books can be placed on the lectern to be read.