The Holy Ghost is a member of the godhead but not equal to Heavenly Father. “The Holy Ghost is the third person in the Godhead. As such he possesses the power of Deity. However, he is not fully like the Father and the Son in that he does not have a body of flesh and bones. He is a personage of Spirit” (Sharing the Gospel Course Manual, p. 104). “He is a spirit that has the form and likeness of a man (see D&C 130:22). He can be in only one place at a time, but his influence can be everywhere at the same time” (Gospel Principles, p. 37).
Biblical Christianity teaches that the Holy Spirit is God, equal to the Father and the Son. His knowledge, power, and presence have no limits.