The full name of the circle method was "Hardy–Littlewood circle method". It was not only an important tool for the Goldbach's conjecture but also an important tool for analytical number theory.
The intended use of this tool was not necessarily for Goldbach's conjecture. It was now widely believed in the mathematical analysis community that this concept first appeared in Hardy's research on "symptomatic analysis of integer splitting". When Hardy and Littlewood collaborated on the Hualin issue, this method was fully completed.
As an important tool for studying Goldbach's conjecture, this method had been expanded by other mathematicians.
For example, Helfgott who stood on stage was one of the contributors to the circle method.
"… The meaning of the Goldbach's conjecture is that any even number greater than 2 can be written as the sum of two prime numbers. We can call this guess A."