A few years ago, Zendesk acquired a chat company called Zopim, which was renamed Zendesk Chat. After the acquisition, most customers were migrated to Zendesk Chat. However, some are still using a legacy version of Zopim.
Follow these instructions to install each app:
Note: there isn’t a third app for Talk because Zendesk Talk is built into Zendesk Support. That means Zendesk Support automatically tracks Talk activity.