Assembly of God is more of a Charismatic movement with less noise and less of the slaying in the spirit and speaking in tongues, depending on where you go, though it has a lot of Pentecostal beliefs. In a Church of God (Cleveland, Tennessee) it is all out Pentecostal and they run the aisles, speak in tongues, slay in the spirit and other things. Don't get the Church of God's mixed up though if you are looking for one. I am a member of the Anderson Church of God and it is evangelical with liturgy. Though they typically believe in the gifts of the spirit, they don't practice them much if at all.
Both the AG and the COG (Cleveland) are classical Pentecostal. Both denominations have their fair share of PINO congregations (Pentecostal in Name Only).
I know that in the world are different Pentecostal movements , but I don't understand what's the difference between the Church of God and Assemblies of God ? I'm a Pentecostal member of The Free Church of Jesus ( AoG ) in Romania I was part of CoG , I se no difference
I live in the USA, so my answer reflects American realities. I make no claim as to what things are like in other parts of the world.
The difference is cultural, theological, and organizational.
Culturally, the Church of God (Cleveland, Tennessee) originated within the Southern United States (particularly the Appalachian regions). The Assemblies of God from it's beginnings has always been more spread out geographically. Therefore, the AG never was dominated by one cultural orientation like the COG was for many decades.
Theologically, the Church of God (Cleveland, Tennessee) is Wesleyan-holiness. It has traditionally believed in 3 major "crisis" moments in the Christian life: the new birth, entire sanctification, and the baptism in the Holy Spirit.
The AG is non-Wesleyan in its theology. This is called Finished Work Pentecostalism. Essentially, the AG denies that there is such an experience of entire sanctification. It believes that sanctification is a process.
Organizationally, the two denominations are different. In the Church of God, authority is heavily centralized in the hands of national and international bureaucracies. Local churches are clearly subordinate to the national and international church bodies.
The AG has national bureaucracies as well, but pastors tend to be more independent than COG pastors. Local churches are said to be "sovereign" and affiliation with the General Council is said to be "voluntary" (however in recent years the national AG leadership has tried to keep churches from taking their property with them when they leave the General Council).