Let's look at the full verse
"But ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should show forth the praises of him who hath called you out of darkness into his marvellous light." - 1 Pet. 2:9
There's no doubt that the Church of Christ is an Ecclesia, which means a Body, and that Christ Jesus is the Head of this "Church, which is His Body." (Eph. 1:22,23.) It's clear that different members of the Church are being called – chosen from the world of people. The Scriptures also clearly show what the purpose of this call is. The Apostle Peter mentions that the Church is a group of people with a special purpose; God has a specific reason for choosing the Church. They are meant to "show forth the praises of Him who hath called them out of darkness into His marvelous light," so that others can see their good deeds and honor their Father in heaven. – I Pet. 2:9; Matt. 5:16.
You ask, "what is called?", obviously the Church. Another question should be about the purpose of this shining light, and the Scriptures tell us that it will impact the world, correcting people and providing an example of how to live and think better. Is this the final purpose of "the call" (1 Cor. 1:26). The Scriptures say it's not; the Church is called to be a special group and to become joint-heirs with her Lord in His Kingdom, Yat the end of this Gospel Age, He will return, not as a Sin-Offering, but as a great King, Prophet, and Judge, to share the blessings earned by His death. What is the Church's role right now? The answer is that those who faithfully follow the Lamb through good times and bad, who take up their cross and follow Jesus, will be seen as worthy to be His partners in the Kingdom.