What is this election for?

New Jersey state law provides for semi-closed primaries, meaning that a voter must be registered as a party member in order to participate in that party's primary.
An unaffiliated voter can participate in the primary of his or her choice by affiliating with a party on the day of the election – in other words, by voting in either party’s election on Election Day.
To become unaffiliated again, a voter must file a Political Party Affiliation Declaration Form 55 days before the next Primary Election. The form can be mailed or delivered to the Commissioner of Registration in the voter’s county or filed with the voter’s municipal clerk.