Using the "project-rules" in 0.45.2

I still dont know how it work …
how it aotu select what is useful ?

some keywork input to the composer ,then it would auto find the right information from project-rules?

“When you specify file patterns here (e.g. *.tsx), this rule will automatically be included in AI responses for files matching those patterns”

the desc means when composer decide to change some files, it would firstly to find out those files fixed the partern content rule ? and how can i konw it actually get the right rules?

can u show me an example ,pls ,thx