Genesis 2:18

"The Lord God said, 'It is not good for the man to be alone. I will make a helper suitable for him.'"  Genesis 2:18

In defining "a helper suitable" the Qbible uses the word "complement."  So the helper for man will be his complement.  This counterpart is more than just a helper, it's the perfect match for him.  The New Revised Standard translates this as "a helper as his partner."  And the International Standard as "I will make the woman to be an authority corresponding to him."
 
Here's a footnote from usccb.org that explains very well:  "lit., 'a helper in accord with him.' 'Helper' need not imply subordination, for God is called a helper (Dt 33:7; Ps 46:2). The language suggests a profound affinity between the man and the woman and a relationship that is supportive and nurturing."  This article points out that man recognized that she belonged to the same category as he did.  Man is incomplete without woman.  And this article states, "Man was made to manifest God's authority; woman was made to manifest man's authority. The woman is a vice regent if you will who rules in the place of man as it were or carries out man's will as man rules in the place of God and carries out God's will."

It's good to realize that "helper" doesn't mean that woman is inferior to man, that God created man and woman together as equals, so they wouldn't be alone.