In simple term, God has 3 titles and these 3 titles are assigned to 3 Persons who carry different functions. All these 3 Persons are united by the same Spirit.
John 16:15 Jesus says: All that the Father has is mine; therefore I said that He (Holy Spirit) will take what is mine and declare it to you.
Echad in Hebrew means plural of persons united as one in unity. Echad God is not physically one as God is Spirit. He can manifests as 3 persons at the same time that is why He is called God!
What is the Trinity? Is the True God a Trinity? Is Jesus the Jehovah YHVH? Please view it and comments on the arguments presented.