WebsitebeginnerFree
Group Properties Wiki
Groupprops (Group Properties Wiki)
The Groupprops wiki entry on group actions, giving equivalent definitions, related notions such as orbits, stabilizers, transitive and faithful actions, and links to many worked examples and facts. Readers can use it as a precise reference while studying group theory.
More resources on Group Actions
WebsiteFree
Wolfram MathWorld
MathWorld is an online mathematics encyclopedia from Wolfram Research offering detailed, browsable articles on topics across the math spectrum, including algebra, geometry, calculus, and number theory. Each entry includes definitions, theorems, formulas, diagrams, worked examples, and links to further reading.
CourseFree
Abstract Algebra
Learn group actions with Prof. Benedict Gross! This abstract algebra course explores key concepts with clear explanations.