.csv files present data in a tabular format, most commonly this type of file is accessed as a spreadsheet via Microsoft Excel or Google Sheets. Information presented in this way can be also be used to import large lists, such as when creating a mailing list in a service such as Mailchimp.
With Bookwhen you can export 3 different sections in .csv format -
Attendances - Accessed via the Bookings tab by clicking on the options - export attendances. This will give you a file showing all of the attendances from the period defined by the search filters you have selected. You can access a key explaining the columns included on the attendances export here.
Bookings - As above, these are accessed via the Bookings tab, according to the filters applied there. This export will give you all of the bookings placed by your customers in this period. You can access a key explaining the columns included on the bookings export here.
Customers - Accessed via the Customer list, this export will give you information on all the customers that match the filters you have applied here (to download all of your customers simply leave the filters blank). Click options - export customers to download.