A seat, which could refer to any form of place to sit, with the distinction that a seat is generally fixed, and is not a chair which can be moved.
This emoji is intended to be a seat on some form of mass-transit, such as on an airplane, train or bus. Google previously displayed this as an orange wooden chair.
Seat was approved as part of Unicode 6.0 in 2010 and added to Emoji 1.0 in 2015.
U+1F4BA
? Seat