What is the different between filter and segment?

[IvanN]

For filters, when you make an API request you get back entries of data
which represent rows in a table. Adding a filter simply includes or
excludes rows of that final table.
Segments operate at a lower level. Currently Google Analytics collects
a stream of "hits" (pageviews/events/etc) which are associated with a
session. Each dimension and metric Google Analytics exposes can be
represented as a function where the parameter is all the sessions in
the selected date range.