When you anonymize data, you remove or change enough information in a data set to ensure that no single – or a combination – of values can be used to identify a person. This is useful when you need to share data, but do not have consent for sharing the identity.
There are multiple ways to anonymize data, and how you do it depends on your situation and field of research. E.g. if the population of people is small, you might be able to identify a person by combining other values like age and city even though the name is deleted.