It's stuff like not having to worry that your name sounds a bit too "ethnic" on a job application. Not having to worry too much when you get pulled over by the police. Not having to second guess whether the neighbours might be hostile when you move to a "nice" area. Not having teachers who expect you to fail, or who categorise every daft mistake you make as a fundamental part of your character just because of the colour of your skin. Not having people look at you sideways in crowded streets in case you're up to no good. All the time. Because pigment. Not having to grow up in an area which is considered a ghetto because that's where your grandparents could afford to live in the 1950s. Not having to deal with shock from everyone you encounter if you manage to overcome the fairly heavily stacked odds to make a success of your life. Or if it's not shock, the assumption that you must either be a rapper, a drug dealer or a footballer, because what else can black people do, right? (I nicked the last one off Marcus Rashford- don't shoot me).
And most of all, the privilege of not even having to be aware that this is what our country looks like to about 13% of the people who live here.
I'm very white by the way, but live in quite a mixed area. Which I love.