Please explain in English what being HER2 positive means?

[skoolmom]

I'm having a hard time explaining to friends and relatives what it actually means to be HER2 positive, I am ER,PR negative and I can explain that my cancer isn't estrogen driven that's easy to explain. I had four rounds of A/C and I had 4 weeks of Taxol/Herceptin - only 8 more weeks to go on the Taxol! I know that Herceptin is the miracle drug for those of us with HER2 positive and that I will be on that for a year or more if the trials prove that it is best to stay on it longer than one year. Maybe one of you have an easy to decipher explanation of what being HER2 positive actually means. Thanks for all your responses to my other questions I love this website and all of you! I posted this website on my onc's bulletin board and told everyone I have chemo with about it. I pray for all of us everyday, God Bless!