What does this mean is simple terms?
What does a person "receive" exactly when they receive Christ? Explain this process and what happens.
And what does this mean? Baptizing is a physical ritual, so explain this claim.
The righteousness of God is the Spirit of God. The Spirit of God is holy.
In the OT, we get glimpses of the spiritual presence of God dwelling amongst men, as in the tabernacle and in Solomon's temple. There are also encounters with the Lord, had by Abraham, Moses and others. All these encounters confirm the holy nature and power of God.
When God gives men his law, the law is good because its author is good. But law is intended to discipline the behaviour of a man's outward actions, not his inner Spirit. For example, one of the Ten Commandments states that 'Thou shalt not commit adultery' [Exodus 20:14]. This is the law. To be righteous under the law, one must not commit adultery (or break any other commandment).
When Jesus appeared, he set an even higher standard. He said, 'whosoever looketh on a woman to lust after her hath committed adultery with her in his heart'. [Matthew 5:28]
Wow! Suddenly, people start asking, Well how can we possibly hope to be righteous if the bar is set so high?
Now you got it. You can't do it without the Spirit of Christ!
We're all sinners because we all fall short of the glory of God. No one is righteous in the sight of God except...Jesus Christ. Why? Because he was, and is, 'God with us'.
To be baptised in the Spirit means that you receive the righteous Spirit of Christ. It's not ours to boast about! It's grace, a free gift.