This tool returns words which are in some way related to your search query. If you have any feature suggestions, please send them to me!
Related Words runs on several different algorithms which compete to get their results higher in the list. One such algorithm uses word embedding to convert words into many dimensional vectors which represent their meanings. The vectors of the words in your query are compared to a huge database of of pre-computed vectors to find similar words. Another algorithm crawls through Concept Net to find words which have some meaningful relationship with your query. These algorithms, and several more, are what allows Related Words to give you... related words - rather than just direct synonyms.
As well as finding words related to other words, you can enter phrases and it should give you related words and phrases, so long as the phrase/sentence you entered isn't too long. You will probably get some weird results every now and then - that's just the nature of the engine in its current state.
There is still lots of work to be done to get this to give consistently good results, but I think it's at the stage where it could be useful to people, which is why I released it. If you have any feature suggestions, bug reports, or comments about the site, I would really love to hear them! You can send me an email here. Thanks!