What is the difference between יצירה, בריאה, and עשייה? (Three terms for creation). The first is used in Genesis (1:1), the second in Genesis (2:7), the third in Genesis (1:11).
The Ri ibn Shuaib explains in a d'rasha on B'reishis that בריאה refers to creation ex nihilo, יצירה refers to creating a basic form, and עשייה refers to completing and arranging a thing in its final state:
ומלת בריאה, פירשו בו ז"ל, הוצאת יש מאין. ויצירה, ציור הדבר. והעשיה גמר הדבר ותיקונו.
R' Aryeh Kaplan provides a similar explanation in his Sefer Yetzirah: The Book of Creation in Theory and Practice (p. 43):
In Hebrew, there are three words which have similar meaning. They are Bara, meaning "to create," Yatzar, meaning "to form," and Asah, meaning "to make." According to the Kabbalists, Bara indicates creation ex nihilo, "something from nothing." Yatzar denotes formation of something from a substance that already exists, "something from something." Asah has the connotation of the completion of an action.101
The Vilna Gaon in Aderes Eliyahu at the beginning of Parshas Bereishis says b'riah is חידוש העצם, the creation of the "essence" of the object, yetzira is צורת הדבר בכמות, giving its dimensions or shape, and assiya is תיקון עשייתו, the set-up or preparation of its ongoing existence (the Gaon uses תקון to mean this in several contexts).