Yes, Log Analyzer is a module that you install on the main Orion server and then it can also be installed on additional polling servers to collect syslogs, traps, Windows Events and even VMware Events if you have a license for Virtualization Manager. There is a .pdf version of the admin guide located here: https://documentation.solarwinds.com/archive/pdf/la/LA-Admin-Guide.pdf
Also, just to clarify... In your question you mentioned Log Analyzer and LEM. LEM is actually a different product which has been renamed Security Event Manager.