Elaborative encoding is a type of mnemonic in which new information is made memorable in order to be able to recall it more easily. It is making information more elaborate and complex in order to be more likely to remember it in the future. This is typically done by relating it and connecting the new information to already existing knowledge.
Examples of elaborative encoding include the peg word system and the method of loci ways of recalling information. An easy example would be meeting a person for the first time whose name you need to remember. Let's say their last name is Fisher. A method of elaborate encoding would be envisioning the person wearing a silly fishing hat and holding a reel as you mentally repeat their name a few times. This elaboration of their name with already existing knowledge about 'fishers' make the new information more salient and therefore makes you more likely to remember their name in the future.