"We’re dealing in a world of espionage, we’re dealing in a world of hidden identities. [John David Washington] is playing an operative who is known by the term ‘Protagonist. Tenet is the name of the organization into which the Protagonist gets inducted. Robert Pattinson’s character is called Neil or, more unhelpfully, “we think he may be called Neil.” He is a “slightly rascally character who operates within what they refer to as this twilight world of operatives in different secret services.”
https://www.gamesradar.com/tenet-mea...r-nolan-movie/