The $offset parameter is most often used in conjunction with $limit to page through a dataset. The $offset is the number of records into a dataset that you want to start, indexed at 0. For example, to retrieve the “4th page” of records (records 151 - 200) where you are using $limit to page 50 records at a time, you’d ask for an $offset of 150:
https://soda.demo.socrata.com/resource/4tka-6guv.json?$limit=50&$offset=150