The LMS is the Open edX tool that learners use to access course content, including videos, textbooks, and problems, and to check their progress in the course. The Open edX LMS can also offer a discussion forum and a wiki that both learners and course team members can contribute to.
For course team members, the LMS includes an Instructor Dashboard, with options to enroll learners, produce reports, and administer a course as it runs.
You use the LMS directly through a browser. You do not need any additional software.