The incel movement is a nebulous term used to identify a currently non-existent (outside Germany) cohesive, self-conscious movement that seeks to create a better future for men who under the current system are not able to obtain sex.
It is important to clarify the the word incel itself does not imply a movement. There also really isnt any cohesive political, cultural, or societal project to help incels outside the Absolute Beginner community in Germany. All other incel communities are just dedicated to shitposting, humor, and sperging out about not-so-hidden truths about dating (because feminists wont acknowledge some basic truths about dating).
An incel movement would theoretically be more goal-oriented as producing change rather than as only serving as a brotherhood or support group. An incel movement would also more inclusive, allowing for incel sympathizers who are not themselves incels to be part of working for change.