mastering is the last step in the process of recording a song.  I mastered all my songs myself but there are people that do nothing but mastering with more expensive and much better gear and tools that I have available for my use.  I am in the process of getting my songs mastered by a professional engineer now and hopefully they will be ready soon.  Once they are I will post them on here for download.  They should sound better but I would definitely welcome any feedback from any of you about how you think things sound, etc.