While using Yandex.Audience, you will come across the following terms:

Anonymous identifier (deviceid or cookie)
An anonymous identifier can be the unique identifier for a user's mobile app or a browser. These identifiers become active when someone uses their app or browser. When updating segments, the inactive anonymous identifiers are removed from the segments and new ones are added (for example, if a user purchased a new device or resinstalled an app) so that the only anonymous identifiers present in the segments are the ones that have been active in the past 30 days.
Segment coverage
This is the number of anonymous identifiers of users found in a segment. Due to the fact that one person can use several different devices, apps and browsers, the number of users found and the number of anonymous identifiers of users found in segment coverage may not coincide.
Pixel coverage
This is the number of found anonymous identifers of users which viewed an ad (or ads) containing a tracking pixel.
Own data
This is data on users which is uploaded by the advertiser, such as phone numbers, email addresses, or mobile device IDs. A file containing this sort of data must meet the file requirements.
This is the number of entries from a file containing an advertiser's own data for which the system has found matching anonymous identifiers.