Islam is in itself a Moderate religion, it doesn't allow extremist. Be kind and forgiving... give mankind the right to live in peace and harmony, it is a religion of science and humanity, honesty, integrity, sincerity, forgiveness, equality, and rational and developed thinking
It is a religion that urges for research and development and innovation in various fields of science.. for the invasion of space and sea. it is a religion that urges a Muslim to learn and teach, get educated and create and innovate.. It urges a Muslim to love and forgive, and to respect the other - young and old... This is Islam.
so extremists are not practicing Islam, but use it to justify their actions, they follow their interests in the name of Islam.
"Allah forbids you not, with regard to those who fight you not for (your) Faith nor drive you out of your homes, from dealing kindly and justly with them: for Allah loveth those who are just." (Quran 60:13)
so moderate Muslims are those who follow and practice Islam in all their actions and in every aspect of their life.