The Term "Copts"
The term "Copts" is equivalent to the word "Egyptians." From the Arab conquest until today, this term refers to the Christian Egyptians to distinguish them from the Muslims.

So a Copt is a native Egyptian Christian. Copts are Egyptians whose ancestors embraced Christianity in the first century. The word "Coptic" was originally used in Classical Arabic to refer to Egyptians. In general it has undergone semantic shift over the centuries to mean more specifically Egyptian Christian after the bulk of the Egyptian population converted to Islam. In modern usage, it is frequently applied to members of the Coptic Orthodox Church regardless of ethnic origin.

The Coptic Christian population in Egypt is the largest Christian community in the Middle East. Christians represent around 10-15% of a population of over 80 million Egyptians, though estimates vary. Around 90% of them belong to the native Coptic Orthodox Church of Alexandria. The remaining (around 800,000) are divided between the Coptic Catholic and the Coptic Protestant.