The Word that describes this purpose is "Worship". The Church exists to worship God. How do we worship God with all our heart? Simply by worshiping Him.
The Bible says, "Worship the Lord your God, and serve Him only" (Matt4:10). Notice that worship comes before service.
Worshipping God is the Church's purpose. Sometimes we get so busy working for God, we do not have time to express our love for Him through worship.
Throughout the scripture, we are commanded to celebrate God's presence by magnifying the Lord and exalting His name. Psalm 34:3. We should not worship out of duty; but because we want to. We should enjoy expressing our love to God.
The Word used to describe this purpose is ministry. The Church exists to minister to people. Ministry is demonstrating God's love to others by meeting their needs and healing their hurts in the name of Jesus.
Each time we reach out in love to others, we are ministering to them. The Church is to minister to all types of needs: spiritual, emotional, relational, and physical. We as a Church must equip the saints for the work of ministry (Ephesians 4: 12).
The Church exists to communicate God's Word; our mission is to evangelize to the world. Christ gave us five great commissions, one in each gospel, as well as the book of Acts (Matt 38:19-20, Mark 16:15, Luke 24:47-49, John 20:21, Acts 1:8). As long as there is one person in the world who does not know Christ, the Church has a mandate to keep growing.
Puts a person into the body of Christ. We were called to belong, not just believe (Ephesians 2:9).
This is referred to as discipleship. The Church exists to edify, or educate God's people. This process begins when a person is born again, and continues throughout the rest of their lives. (Colossians 1:28).
Jesus included all five of these elements in His work (John 17). Paul not only fulfilled these, he also explained them in Ephesians 4:1-16)
Acts 2:1-47 They taught each other, they fellowshipped together, they worshipped, they ministered, and they evangelized.
This is the Rivers of Living Waters Ministry's mission:
To Bind up the broken-hearted
To proclaim liberty to the captives
Open prisons to them that are bound
Comfort all that mourn and proclaim the acceptable year of the Lord
(Isaiah 61:1)