Is grand theft auto online a sequel or standalone game?

The evidence describes Grand Theft Auto as an action-adventure video game series developed by Rockstar North and published by Rockstar Games. It outlines the series' focus on open-world gameplay, missions, driving, and shooting. However, the provided excerpt does not include specific details about Grand Theft Auto Online or its relationship to other titles in the series. Without explicit information confirming its status as a sequel or standalone game, the answer cannot be determined from the given evidence.