The most recent understandable implementation of this is something called Word2Vec. It is not the state of the art (it's actually suboptimal now by a lot) but there's a LOT of explanations of it you can find that are great.

A decent video covering it from a programmers perspective (where I'm coming from) https://www.youtube.com/watch?v=LSS_bos_TPI

From a math perspective there's also good materials.

Essentially Apple + Tree != Apple + Computers allowing you to differentiate search like this.