# Contacts

Contacts are the basis of all customer data in Airship. Contacts records can store all sorts of data such as contact information and personal details. A contact record can also have any number of transactional records attached to them to represent a contact's timeline of interactions. For example, Table Bookings, WiFi interactions, Feedback, Purchase History and more.

### Contact merging

Airship automatically merges contact records together based on unique customer identifiers. These identifiers are `email` or `mobile_number`. In other words, if you write a contact to us with an email address or mobile that already exists as part of a contact on Airship, we'll automatically update and/or append the data you send to the pre-existing contact record.