Why is it called "the UK"?

Wait, is it the UK?🇬🇧 Is it England?🏴󠁧󠁢󠁥󠁮󠁧󠁿 Is it Great Britain? I am confused! Well, look no further! I am going to explain the difference & what each name means below⬇️.

Britain - name of the island🌴 England - country occupying the center & southeast part of the island🏴󠁧󠁢󠁥󠁮󠁧󠁿 Scotland - country occupying the northern part of the island🏴󠁧󠁢󠁳󠁣󠁴󠁿 Wales - country occupying the southwest part of the island🏴󠁧󠁢󠁷󠁬󠁳󠁿 Great Britain - political union of the island’s 3 countries: England, Scotland, & Wales✨ United Kingdom - adds the 4th country, Northern Ireland to the political union🇬🇧 British Isles - The islands, which also includes the independent Republic of Ireland🇮🇪 British Commonwealth - former colonies (including Canada, Australia, and India) that profess symbolic loyalty to the crown👑