Thank you for all your replies! I understand it a lot more now!
Maybe this can be of additional help.
Jesus chose and appointed His apostles to take His gospel to all the nations of the world according to the Bible. Peter ended up in Rome. Thomas went to India. One of the James went to what is now Spain. Andrew or Phillip went to Africa and so on.
They all preached the same message, the same doctrine, but these areas are remote from one another and were isolated. There was no radio, telephone, or means of communication between one and another. They were essentially isolated from one another yet they all had the same belief, or faith.
The way this one faith is expressed, the style of how they pray and worship developed differently in different places.
Scripture tells us that the Church has ordained ministers, bishops (episcopoi), priests (presbyeters), and deacons. All the churches throughout the world have people who hold these positions or offices with authority to teach, as Jesus commanded in scripture, for all time. They teach the same gospel wherever they are, the same spiritual truths taught to the apostles by Jesus.
We learn the faith that is passed on from generation to generation.
The definition of apostle is one who is sent. The Church is sent by Jesus to all the nations of the world to preach His message of salvation. It is the same message wherever you go, but if you go into a church in India, brought there by the apostle Thomas, or Spain, brought there by James, and listen to the prayers and hymns they will be different in style. This difference is only a matter of style or culture, not difference in doctrine. It is everywhere the same faith Jesus taught His followers and can not change for all time.
The word catholic is a Greek word that means universal. The message and truths of salvation are universally the same everywhere and for all nations and people. Whether you are an African tribesman, an Eskimo seal hunter, a Chinese merchant, an American engineer, or a Hawaiian hula dancer, the same message applies to you. He told them to “go to all nations and preach the good news of repentance for forgiveness of sins”. Wherever and whomever you are, you are sinful and God’s mercy is yours if you turn from your sins. Nothng has changed from the time of Jesus. This simple universal (catholic) message is still the same everywhere, preached by His Church, and each person can take it or leave it.