From the site:
New Yorkers have been providing their ideas on creating a greener, greater New York. This is your chance to pick the ones that best represent your priorities. Please select one idea from the two choices below. Two new choices will appear and you will get to choose again. Also, you can add your own ideas by clicking the green button below.
According to one article:
Using All Our Ideas, New York City residents have contributed more than 21,000 votes and more than 200 new ideas for PlaNYC 2030, in less than three months.