[^a]* meaning of it in example

ne.jpg

bit
bar
baer
bear
ber
bir

baaaar
beeer
biir
br
brr

bat
bit

why did it not choose bit ???

In v4.1.2.2 the term [^a]* does select “bit” if you have the Regular expressions option checked. The meaning:

^a == any character that is not a lower case “a”.

[]* == match the expression in the brackets 0 or more times.

Thus, the first match is “bit b” then the “a” is not matched, the next match is “r b”, then the next “a” is not matched, the next match is “er be”, then the next “a” is not matched, and so on. If you change the expression to b[^a]*r as in your screenshot, then as @karolus indicated it will not match “bit” as it ends with a “t” rather than an “r”.