Blocks are created through the process of @mining, and the @node that successfully mines the block then broadcasts it to each of the @nodes connected to it, who subsequently re-broadcast the block until the entire Monero network has received it.
Fake or bad blocks generally cannot be created, as @nodes that receive blocks always verify the @transactions they contain against a set of consensus rules that all nodes adhere to, including validating the cryptographic @signatures on each transaction.
