Yes. Responses can be anonymous or anonymised. There are different ways to allow or create anonymous responses.
Anonymize from the Manage Project/Customise/Advanced tab in a project. When a participant submits their survey responses their personal details and email address are automatically anonymised.
The anonymize option can be applied at any time. Either before, during or after a project is complete.
This feature allows surveys to be distributed with names and email addresses and followed up with email reminders. However, once a participant has completed a survey, their personal details and email address are no longer shown. The participant name is replaced with "Anonymous" and a number but their personal details are not shown.
Also, if a Group Link is set to allow respondents to complete the survey without registering their details, then their responses will be anonymous.
Administrators can turn this feature on and off. Users can anonymise but cannot turn the anonymise feature on.