What is the difference between the Righteous (al-Abrar), the Pious (al-Muttaqin), and the Companions of the Right (Ashab al-Yamin)?

In summary: The Abrar (the righteous) are those who obeyed God and served His religion, thus earning His pleasure. It is also said they are the prophets and the pious, or the sincere believers in their faith. The Muttaqun (the God-fearing) are those who feared God's punishment through their good deeds and supplications. It is also said they are those who fulfill commands and avoid prohibitions, both secretly and openly. The Ashab al-Yamin (Companions of the Right) are those who are given their books in their right hands. It is also said they are those blessed upon themselves. All of them are among God's righteous servants and the people of Paradise.