Star Trek: Picard - 16 Huge Details Everyone Missed In The Trailer
Ok so this is where things are going to start getting a little confusing.
At the end of Star Trek Nemesis, Data sacrifices his life to save Picard. He leaves behind another Noonian Singh robot in the form of B-4. There is also, of course, Data's brother Lore. One of these 3 robots is pictured in the establishing shots of the trailer.
The obvious answer to 'Uh, hang on, who is that?' is that these are the remnants of Data, given that Picard is literally talking about his friend's sacrifice as we see the shot. However the explosion on the Scimitar would likely have entirely vaporised him, so it makes more sense that this is a decommissioned B-4 - Starfleet presumably unable to make him function.
However the problem with both of these assumptions is that, in the current canon, Data is actually alive...
In Star Trek: Countdown, a 4 part graphic novel series that bridges the gap between Nemesis and J.J. Abrams Star Trek (2009), it is revealed that Data has downloaded a part of his consciousness into B-4, and over time was able to successfully reassert his personality. Star Fleet reinstated him, and by the time we last left the story he was captain of the Enterprise.
When last we checked, these graphic novels were officially part of the Star Trek lore. Seeing either Data or B-4 in a drawer somewhere implies that either this is been retconned, or something else has happened entirely.