Remote Submit (RSUBMIT) is part of SAS/CONNECT software. It allows a SAS session to talk to a different SAS session. These SAS sessions can be on different machines (i.e. UNIX and Windows OR LINUX and z/OS). You are able to submit SAS code from one session to a different session; the code will run on the different session; and then the results will come back to the initial session.
RSUBMIT is used with SAS Grid Manager to take a long running SAS job and distribute it across multiple systems (or SAS sessions) to enable the long running SAS job to run faster. Here is an old SAS Global Forum paper that discusses this concept. http://www2.sas.com/proceedings/sugi27/p279-27.pdf The MP Connect feature is this paper is using RSUBMIT statements