It is a language of men or angels. It is inspired utterance. The operation (energizing) of holy spirit within the believer who has received holy spirit upon believing.
Paul exhorted all to speak in tongues much. For it is perfect praise, perfect prayer to the Father. I pray in tongues, and I pray with the understanding, also. He that worships, MUST worship in spirit and truth. Or, more accurately, truthfully via the spirit. Or by speaking in tongues. For speaking in tongues is the evidence of the indwelling of holy spirit given when one believes on the Lord Jesus and believes that God raised him from the dead.
Do all who have received holy spirit speak in tongues? No.
CAN all who receive holy spirit speak in tongues? Yes.
It's a matter of understanding the truth of the matter and desiring to manifest. That you speak in tongues is your desire or will. What you speak is energized by God.