Honey Blocks are acquired by dripping honey onto water (Or Vice-versa.) and mining it, much like obsidian. Touching this block from any side slows down the Player dramatically. It is a material in creating an Abeemination, which will summon the Queen Bee.
When using the Water Walking Boots or any other variation of that ability, stepping onto a Honey Block and then walking onto another liquid will 'cause the player to retain the slow movement speed until they jump or walk onto a different block.