What is the difference between event, visit, visitor and user segmentation?

There are 4 types of segmentation:

Segmentation with an event scope

This type of segment allows you to limit the traffic analyzed to events (Example: I want to focus my analysis on quote validations).

Segmentation with a visit scope

Working on a set of visits corresponding to predefined criteria, over a given analysis period. (Example: visits from sponsored links).

Segmentation with a visitor scope 

This segmentation is based on a cohort notion. A cohort is defined over a period N. It is composed of all visitors that have shared (at least once) the same visit experience during period N. (Example: visitors that came from a sponsored link last week).

All visits made by these visitors meeting these criteria (during at least one visit) will be taken into account during your analysis period.

Segmentation with a user scope 

When the scope allows visitors to connect to a user account, it is possible to use the account ID (CRM ID) as a reconciliation criterion for the cohort.