Difference Between Open Manage Server Administrator and Essential

Hi All, 

 I have tried to find the answer to my question before posting a new topic, but I could not find it, so here I am.

Basically, I would like to know the difference between the Open Manage Administrator and Essential, 

(OMSA and OME). Are they different in their functionality? 

Why am I asking this? 

We have servers running a  third application and we need to monitor the system regarding hardware and we are not sure which tool need to be installed, not only that, but also if this application can be installed without restarting the system and if it could cause any impact on the application already installed on the server. 

Are any particular PORT used by these applications? 

Thank you for your comprehension and if anyone could help me, I would appreciate.