A lectern is a reading desk, typically free standing (though sometimes they can be smaller items, placed on a table-top), from which speeches, lectures or public announcements are given. The word comes from the Latin legere, meaning 'to read', from whose root we derive the word 'legible'.
Modern politicians' lecterns can be dull affairs, perspex or wood for example, and largely devoid of ornament, but the lecterns in churches, not least those dating from earlier centuries, are often of brass and highly ornamental. The favoured shape for the desk part is an eagle, upon whose back and spreading wings a large Bible can be placed. The eagle is the creature associated with St John the Evangelist, and by tradition symbolises the exalted level of his writing in the first chapter of his Gospel, which begins "In the beginning was the Word, and the Word was with God and the Word was God..."
On a personal note I first learned of the association of the eagle with St John from a Tintin book, Red Rackham's Treasure. If you are a fan of Hergé's Adventures of Tintin, you will know the part of the story I am referring to. If you have yet to discover the wonders of Hergé's work, I could not possibly spoil the plot for you.