Daniel 8:15 (ESV)

15 When I, Daniel, had seen the vision, I sought to understand it. And behold, there stood before me one having the appearance of a man.

Daniel sees God’s vision and there is much that is not clear to him. He requires an explanation. The Lord does not give this vision so that it remains obscure forever, but rather he takes care that Daniel receives the proper explanation so that it can be passed on. There is an angel standing next to Daniel who will give the explanation on God’s behalf.  This angel looks like a human being, as did the angels who came to Abraham along with the Lord in Genesis 18:1–33. Also when Jesus Christ shows the apostle John something of the future in a vision, there is an angel who explains and clarifies matters. See for example Revelation 19:9–10.