The book of Revelation mentions seven spirits near the throne of God. They are not on the throne, but they are "before the throne." In this position of subjection to God, they are at His service. This cannot describe the Holy Spirit. Besides, the Bible says there is only one divine Spirit (Ephesians 4:4), not seven.
The best way to understand this Biblical expression is, as always, to compare Scripture with Scripture. In other words, find other verses that give us more information about it. I've done that, and I'd like to share what I found. Click on the link that follows for a comparison of verses from which we can conclude quite certainly that these spirits are seven angels who stand before God.
The Seven Spirits