From Halopedia, the Halo wiki
The unidentified interviewer is a man who interviewed several retired soldier after the Human-Covenant War.
Around 2595, the interviewer interviewed retired soldier Niraj Shah at a site of a battle during the Battle for Earth where the ceremonial grave of the John-117 was at.
The interviewer also interviewed John Tippett, at another site of the Battle for Earth where Tippet was stuck for seven hours where the Covenant was hunting him and his Platoon.
The interviewer interviewed Roland Huffman and Tomas Navarro in the "Weapon room" of the Museum of Humanity.
After the John-117 Monument was completed in 2610, the interviewer interviewed Pawel Czernek near the model, talking about the events depicted in it.