While there is an objective moral standard which most people understand, it is by no means always observed. It is common for people to violate the eternal moral standard. The Bible has a term for a violation of the moral standard - it is called “sin”.
Sin is committed whenever we do something we should not do, or whenever we fail to do something which we should do. Any person who commits sin - breaks the moral principle - is described as a sinner.
And everyone is a sinner. We know this from personal experience; we can all remember times when we have done things of which we were later ashamed. There will be other times when we did things that were wrong, but where we have not remembered them. The Bible says this:
"What then? Are we Jews any better off? No, not at all. For we have already charged that all, both Jews and Greeks, are under sin, as it is written: 'None is righteous, no, not one;'" (Romans 3:9,10)
This is the beginning of a passage which summarises the teaching of the Old Testament on the subject by producing a long list of verses. These begin with the above and end at verse 18. The whole is summarised a little further on:
"for all have sinned and fall short of the glory of God," (Romans 3:23)
We know that this is the case, and it has consequences. The creator of the universe is intimately concerned with moral standards, and we have violated those standards.