What is Wahdat ul Wajood?

Many people asked that What is Wahdat ul Wajood? They asks such kind of questions:
1. Is Wahdat ul Wajood a religion?
2. Is Wahdat ul Wajood a theory?
3. Is Wahdat ul Wajood a philosophy?
4. Is Wahdat ul Wajood a believe or a blind faith?

Wahdat ul Wajood Proves the Oneness of ALLAH. As ALLAH said in the Holy Quran, "ALLAHU NOOR-US-SAMAWATE WAL-ARD".