Ibid. is a short Latin label you meet in formal writing, most of all in the small notes at the bottom of a page. It means “from the same book, the same writer, or the same article I just named.” So if you point to a book on one line, and the next note is still that book, you can write ibid. instead of writing the whole name again. You may add a new page number: ibid., p. 55. Though actually, this is a paper tool, not a speaking word. Nobody says ibid in a shop or a chat. Some teachers now ask students not to use it, because if you later move a paragraph, “the same book as above” can point to the wrong line. It still appears a lot in older papers and in some university styles. It feels very formal — a little dusty. Say it as two short bits, “ib-id.” It is usually written with a full stop: ibid.