Is this correct? Trust= the ones you purchase from Marriott and Legacy= the ones you get in exchange for your timeshare week for the destination program?

This is correct. Legacy points are what you get for converting an enrolled legacy week to points.  Marriott actually calls these Elected Points.Trust points are purchased from Marriott on or after 6/20/2010. If you own trust points, you own beneficial interest in the trust. Each BI is equal to 250 points.