In the Meeting Center you will be using your "Personal Room" to conduct the meeting. Meeting Center should be used for smaller groups of people or single meetings. You can schedule a meeting for future dates, Schedule a Meeting, or create a meeting on the fly, Meet Now. The link that you give to participants will always be the same, but the participants will not be able to enter the room unless you are present.
In the Training Center you can schedule a single meeting, Instant Session, or re-occurring meetings, Schedule Training. Training Center should be used for larger groups of people as you have more control over the meeting settings, like muting upon entry. The link you give participants is only good for that session. Once the session is over, the link will not work (unless it is a re-occurring meeting).