This definition of LMS from Wikipedia is an excellent introduction :-
A Learning Management System (LMS) is software for delivering, tracking and managing training.
LMSs range from systems for managing training records to software for distributing courses over the Internet
and offering features for online collaboration.
They provide registration of students, eg employees, for classroom and online courses.
Student self-service (e.g., self-registration on instructor-led training), training workflow (e.g., user notification, manager approval, wait-list management), the provision of on-line learning (e.g., Computer-Based Training, read & understand), on-line assessment, management of continuous professional education (CPE), collaborative learning (e.g., application sharing, discussion threads), and training resource management (e.g., instructors, facilities, equipment), are dimensions to Learning Management Systems.
LMSs are used by regulated industries (e.g. financial services and biopharma) for compliance training.
Some LMS providers include "performance management systems," which encompass employee appraisals, competency
management, skills-gap analysis, succession planning, and multi-rater assessments (i.e., 360 degree reviews).
For the commercial market, some Learning and Performance Management Systems include recruitment and reward functionality.