A global segment is a segment that always appears in the descriptive flexfield pop-up window, regardless of context (any other information in your form). A context-sensitive segment is a segment that may or may not appear depending upon what other information is present in your form.
A context field appears to an end user to be just another segment, complete with its own prompt. However, a context field behaves differently from a normal flexfield segment (either global or context-sensitive). When a user enters a context value into the context field, the user then sees different context-sensitive segments depending on which context value the user entered. You define a context field differently as well. You use a context field instead of a reference field if there is no form field that is a suitable reference field, or if you want your user to directly control which context-sensitive segments appear.
A context-sensitive segment appears once the appropriate context information is chosen. The context-sensitive segments may appear immediately if the appropriate context information is derived from a form field before the user enters the descriptive flexfield.
For a descriptive flexfield with context-sensitive segments, a single "structure" consists of both the global segments plus the context-sensitive segments for a particular context field value. That is, a structure consists of all the segments that would appear in the pop-up window at one time (after the structure has been chosen).
Different Arrangements of Segments
Planning Your Descriptive Flexfield
Descriptive Flexfield Structure Planning Diagrams