"A born again Christian has a new nature that cannot sin". I have found versions of this statement on this site. What does it mean "practically"?

I have come across this phrase "***A born-again Christian has a new nature that cannot sin***" (or other versions written differently but carrying the same implication). Here is one example from this site and here is another more fulsome treatment from an evangelical perspective. Does this mean a born-again Christian can not sin? If we can still sin, then what is the purpose of that nature if it can not shield us from sin? ***How would/does a nature like this make us different from Abraham, Noah, Job, David or Moses?***