In eSputnik you can distinguish target audience using 3 types of segmentation.
List is a static segment more suitable for a small number of specific contacts. It is created at the stage of contact import, filling subscription form or in automation scenario. You can add contacts to the list manually from existing contacts or by creating new ones.
Conditional segments can be changed depending on conditions. For example, if you create condition Main - Birthday - Next week any year, contacts whose birthdays correspond to this criterion will go automatically to this segment.
Composite segment puts together existing segments. You can send a campaign to subscribers belonging to one or all selected segments. In the same way, contacts from these segments can be excluded.