Who represented "the Lord" in Exodus 4:24-26, and what's the deal with the foreskin?

In [Exodus 4:24-26](http://www.biblegateway.com/passage/?search=exodus%204:24-26&version=NIV) : > At a lodging place on the way, the LORD met Moses and was about to kill him. But Zipporah took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it. “Surely you are a bridegroom of blood to me,” she said. So the LORD let him alone. (At that time she said “bridegroom of blood,” referring to circumcision.) I have 2 questions about these passages: 1. Who was the person referred to as "The LORD"? Was it The Holy Spirit Himself appearing in human form? Was it Jesus? Or someone else? 2. Why did the circumcision and touching of foreskin to Moses' feet apparently satisfy Him?