What does it mean when they say the universe is expanding?

Cosmic expansion is a given. Who inherits the cosmos is not

What is meant by 'The Universe is expanding'? - Quora

Brave New World of Transhumanism

The Universe Is Expanding at an Ever-Increasing Rate

Expansion of the Universe

Expansion of the universe - Wikipedia

Is the Universe Expanding?

The Day Edwin Hubble Realized Our Universe Was Expanding

Expanding Universe, Cosmology

The Missing Piece in the Puzzle of Space, by Rushil, TechTalkers