The SRS (supplemental restraint system) has a fault stored. Your airbags may not deploy in a crash until it is fixed.
Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.
MOT and the airbag light — Since 2018 a lit airbag/SRS lamp is an MOT failure on cars first used after 2003.
Can I reset it myself? — Generic OBD scanners cannot read SRS — you need a manufacturer or specialist tool.