What is a fifth-generation fighter aircraft?

Any conversation about Australia
Any conversation about Australia's commitment to the F-35 Joint Strike Fighter refers to it as a fifth-generation fighter aircraft. But what exactly is a fifth-generation aircraft, and why is it important?

Explained: Shenyang J-31 & 5th Generation Fighter Aircrafts

What does it actually mean when we say 'fifth-generation' fighter?

Europe's Very Own 5th-Generation Stealth Fighter Could Be Just Around The Corner

The Case for Fifth-Generation and NGAD Airpower

5th Generation Fighters; Beyond Lockheed Martin - Asian Military Review

5th Gen Fighters, Stealthy & Lethal

Let IAF test-fly fifth-generation fighter aircraft, India asks Russia - The Economic Times

The F-35 JSF: what is a fifth-generation fighter aircraft?

Make-in-India: Plan to develop 5th-generation fighter aircraft