Differences in names?

"England" is that part of the island of Britain that is neither Wales nor Scotland.

"Great Britain" was the country's name after the Act of Union of 1707. In effect, "Great Britain" is England + Wales + Scotland + a few other scattered islands.

"United Kingdom" was the formal name given to the country after the 1801 Act of Union, which added Ireland to Great Britain. In 1927, after Ireland gained its independence, the UK became "the United Kingdom of Great Britain and Northern Ireland."