Amazon and Microsoft have officially set up the friendship between their two voice assistants, Alexa and Cortana, a year after announcing the partnership to expand the reach and abilities of the competing services.

But how does this relationship of rivals work? To talk to one assistant through the other, customers have to say either "Cortana, open Alexa" or "Alexa, open Cortana." From there, people can talk to the other assistant as usual.

What they don't get is access to each others' data, according to statements from both companies. Data collected from each assistant will be controlled by their respective companies, and covered by their corresponding privacy policies. In essence, they'll refer users to one another rather than sharing their duties.

"No raw data will be shared between companies," Microsoft said. "Once you open Cortana, all voice data goes to Microsoft not Amazon, and once you open Alexa, all voice data goes to Amazon and not Microsoft."