Barring is fretting more than one string, in the same fret space, with the same finger. Think of an A chord (x0222x); it can be barred with the 1, 2, 3, or 4 finger.
We have to get to know our hands & how they can set bars using the bone edge with the variables of angle, pressure, & height. There’s always a solution.
Other general concepts are to bar as little as possible, and to never hold the pressure of a bar for too long.
And then there’s the hinge bar. Check out the video. Are all bars hinge bars?