Where are post translation relationships defined in DB

I would like to know where the relationship between two posts is defined by the polylang plugin (as in one being the different language version of another) if anyone could shine any light on the subject for me please?

I have looked on Google for the answer, although I may be phrasing the question wrong as I couldn’t find anything helpful, although it appears to me, from perusing the database, that the term_relationships table provides the relationship between a post and a language(may be wrong here?) – though I can’t identify the next step which connects two posts of different languages together.

https://wordpress.org/plugins/polylang/