What is legalism?

Please explain "legalism." Is it the same as what "legalizing teachers" promoted in New Testament times?

"Legalism" as promoted by Judaizing teachers (Acts 15:1) taught that a person needed to keep the law in order to be saved. This is different from the commonly accepted (but not Biblically defined) concept of legalism today. Legalism is not a close, careful and complete obedience to the Word of God. That is faithfulness. Legalism goes beyond the Word of God and adds rules and requirements, not for salvation, but as either a test of reality or as a measure of spirituality. It may involve a sincere desire to please the Lord and take the form of "interpreting" what certain verses mean or "applying" Scriptures. Because it is of the flesh (Galatians 5:19,20), it usually demands adherence to its view and allows no time for personal faith to accept or for personal exercise to develop (Romans 14:3)

A.J. Higgins