To be a Christian is to be one who believes and what we believe matters. To that end, the Apostles' Creed is a succinct list of fundamental Christian beliefs. 

The Heidelberg Catechism's question 22 asks, "What, then, must a Christian believe?" and answers, "All that is promised us in the gospel, which the articles of or catholic* and undoubted Christian faith teach us in summary." The answer to question 23, "What are these articles?" is the Apostles' Creed. 

I believe in God, the Father almighty,
      creator of heaven and earth.

I believe in Jesus Christ, his only Son, our Lord,
      who was conceived by the Holy Spirit
      and born of the virgin Mary.
      He suffered under Pontius Pilate,
      was crucified, died, and was buried;
      he descended to hell.
      The third day he rose again from the dead.
      He ascended to heaven
      and is seated at the right hand of God the Father almighty.
      From there he will come to judge the living and the dead.

I believe in the Holy Spirit,
      the holy catholic church,
      the communion of saints,
      the forgiveness of sins,
      the resurrection of the body,
      and the life everlasting. Amen.

The Apostle's Creed comes to us from a second-century baptismal formula (J.N.D. Kelly). What we read today is based on a fourth-century version. It is appreciated for its ability "in sublime simplicity, in unsurpassable brevity, in beautiful order, and with liturgical solemnity" to describe the foundations of Christian beliefs. 

J.I. Packer pointed out that the Creed functions as a syllabus of required catechumens for the Christian to master.

1. The Trinty

2. The Creation

3. The Incarnation

4. The Holy Spirit

5. The Church

6. The Forgiveness of Sins

7. The Christian Hope

Packer concludes, "All that the Creed covers needs to be grasped and taught, as an integral part of the message of the saving love of God."

A contested line in the Creed reads, "He [Jesus] descended into hell." The reason for the line is Ephesians 4:9-10 and 1 Peter 3:19, the latter which states that Jesus "went and proclaimed to the spirits in prison." R. C. Sproul said, "People are making a lot of assumptions when they consider that this is a reference to hell and that Jesus went there between his death and his resurrection." So, we need to be careful when defending or denouncing the clause.

The debate is not new; John Calvin defended the clause, writing, "it contains the useful and not-to-be-despised mystery of a most important matter." We should note that most churches believe that Jesus' descent into hell was to liberate the spirits of OT saints, not to suffer for sins.

A line that often causes confusion among protestants is "I believe in . . . the holy catholic church." Simply put, here, catholic means "universal" and does not refer (exclusively) to the Roman Catholic Church.

The Church is both holy and universal -- these are physical and spiritual realities. The Church is comprised of God's redeemed people from all over the world.

Want to learn more? Check out these resources: 

Affirming the Apostles' Creed, by J. I. Packer 

What We Believe: Understanding And Confessing The Apostles' Creed, by R. C. Sproul 

The Apostles' Creed remains an essential confession of biblical orthodoxy. Christians should make it a habit to include it in their daily devotions and religious practices.