A gathering of people
Ekklesia, pronounced roughly eh-KLAY-see-ah, was an ordinary Greek word for an assembly. It could describe a public gathering in a city, not only a religious group. In Ephesus, for example, the confused crowd stirred up by the silversmiths is called an ekklesia, and the town clerk speaks of a lawful assembly using the same word (Acts 19:32, Acts 19:39).
So the basic meaning is straightforward: people who have gathered. The word does not first mean a church building, a denomination, or a Sunday service. Those things may serve the church, but they aren't the church itself.
But if ye enquire any thing concerning other matters, it shall be determined in a lawful assembly.
Jesus gives the word a centre
Jesus used ekklesia when he told Peter that he would build his church (Matthew 16:18). He was speaking about a people who belong to him and whom even death will not finally overcome. That gives the word its distinctively Christian meaning: an assembly gathered around Jesus, trusting him as the Christ.
You may sometimes hear that ekklesia literally means "called-out ones". The word is related to Greek ideas of calling and gathering, and God certainly calls people to himself. Still, its normal New Testament sense is "assembly" or "congregation". It is wiser not to make more of its word origins than the passages themselves do.
And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
Local churches and the whole church
The New Testament uses ekklesia in more than one closely connected way. Paul wrote to the ekklesia of God in Corinth, meaning the identifiable believers in that city, with all their real struggles and divisions (1 Corinthians 1:2). A local church is not a perfect club. It is a community being formed by Christ.
The word can also include all believers joined to Christ. Paul describes Christ as head over all things to the church, which is his body (Ephesians 1:22-23). So a congregation in a home, school hall, cathedral, or rented room can truly be church, while also belonging to Christ's much larger people.
Unto the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints, with all that in every place call upon the name of Jesus Christ our Lord, both theirs and ours:
What this means in practice
Ekklesia reminds us that Christian faith was never meant to be only private. The first believers devoted themselves to the apostles' teaching, fellowship, shared meals, and prayer (Acts 2:42). They gathered, learned, gave, served, and carried one another through ordinary life.
That doesn't mean every church tradition must look identical. Faithful Christians differ over leadership structures, worship styles, baptism, and other practices. Yet the centre remains the same: the church is Christ's people, called to love one another and grow together in him (John 13:34-35). If you're exploring faith, reading these passages in context can help you see church as a living people before you think of it as a place.