Believers are Priests - Quick & Clear Bible Study

All believers are priests according to the Bible. What does this mean?

Verses used in this study:
Genesis 4:3-5
Genesis 8:20
Genesis 12:7
Genesis 14:18
Leviticus 21:16-23
Hebrews 2:17
Hebrews 9:26
Hebrews 10:11,12
Revelation 1:5,6
1 Peter 2:5,9
Hebrews 13:15
Romans 12:1