What are the basic beliefs of christianity?

This is a great question, but something that almost all Christians (Orthodox, Catholic, Protestant) agree with is the Apostle's Creed. Here it is:

I believe in God, the Father Almighty,
the Maker of heaven and earth,
and in Jesus Christ, His only Son, our Lord:

Who was conceived by the Holy Ghost,
born of the virgin Mary,
suffered under Pontius Pilate,
was crucified, dead, and buried;

He descended into hell.
The third day He arose again from the dead;

He ascended into heaven,
and sitteth on the right hand of God the Father Almighty;
from thence he shall come to judge the quick and the dead.

I believe in the Holy Ghost;
the holy catholic church;
the communion of saints;
the forgiveness of sins;
the resurrection of the body;
and the life everlasting.

Some points to note:

1. Trinitarian formula - Father, Son, Holy Spirit.

2. The Father is the creator.

3. The son is the savior, who was born of the Virgin Mary, suffered, died and rose again. Notice, he is human and divine.

4. Finally, notice the work of the Holy Spirit and the importance of the church.

In conclusion, there are many other Christians groups and therefore there will be more details of theology. However, the basic core will most likely be the same.