Hi, vsms1990!

Research them for what purpose, please? There's a lot of information out there on the Internet about them. Please click on the following link.

LINK (http://www.google.com/#hl=en&q=Physics+String+and+M-Theory&aq=f&aqi=&aql=&oq=&gs_rfai=&pbx=1&fp=5673716d440c1f33)

Thanks!