About every 3 years in the state of New Jersey (and on the national level via the NEC), the electrical code changes in some way. This may have an impact on you, your home, and any electrical jobs you may be considering.
For example, it used to be that you could use two conductors (“the black wire”) with a shared neutral (“the white wire”) and both circuits sharing that neutral would have independent circuit breakers. Through code revisions, now those 2 circuits must be on a 2 pole breaker, basically if one shorts or trips so does the other. So how does that effect you, and any electrical contracts you had performed, which do not meet the new code requirements? The code only provides the bare minimums in terms of safety, with safety as its ultimate consideration.
Now, as a homeowner, if you just had electrical work performed which did not meet this new code requirement, you don’t have to rush out and have it all replaced as long as the work you did have performed met the code at the time (i.e., passed electrical inspection, or was performed by a licensed electrical contractor). In this particular instance, the code change was more for the safety of those servicing the system than the end user, but it is indicative of code changes which happen every 3 years.
So as a homeowner, you don’t have to worry about code changes as long as you’re using the services of a licensed electrical contractor who makes it their duty to keep up to date with recent changes in safety requirements.