Infinity War and Avengers: Endgame,

Infinity War and Avengers: Endgame, Thanos’ plan was to eliminate half of all living beings in the universe using the six Infinity Stones.

Why did Thanos do it?

Thanos believed the universe had limited resources but an ever-growing population. In his mind, overpopulation would eventually cause starvation, war, and the destruction of civilizations.

He believed the solution was:

Randomly eliminate half of all life so the remaining half would have enough resources to survive.

Importantly, Thanos wasn't trying to kill everyone. He considered his plan a way to create what he saw as balance.

How did he wipe out half of humanity?

He needed the six Infinity Stones, each controlling a fundamental aspect of existence:

🔵 Space Stone — controls space.

🟡 Mind Stone — controls minds and consciousness.

🔴 Reality Stone — can alter reality.

🟣 Power Stone — enormous destructive power.

🟢 Time Stone — controls time.

🟠 Soul Stone — connected to souls and life.

He placed all six stones into the Infinity Gauntlet.

Once Thanos had all six, he could essentially manipulate the universe with a thought.

The famous Snap

At the end of Infinity War, Thanos fought the Avengers and their allies on Wakanda. After obtaining the final stone—the Mind Stone, which was in Vision's forehead—he completed the Gauntlet.

He then snapped his fingers.

The Stones responded to his command, and half of all life in the universe disappeared.

It wasn't specifically "half of humanity." Humans were only one of the many species affected. Animals, aliens, and other living beings throughout the universe were also randomly affected.

For example, some Avengers survived while others disappeared:

Spider-Man ❌

Black Panther ❌

Doctor Strange ❌

Wanda ❌

Star-Lord ❌

Groot ❌

Nick Fury ❌

while:

Iron Man ✅

Captain America ✅

Thor ✅

Hulk/Bruce Banner ✅

Black Widow ✅

Hawkeye ✅

The selection wasn't based on who was good or bad. It was essentially random.

What happened afterward?

Thanos went to a remote planet and destroyed the Infinity Stones so nobody could reverse what he had done.

Five years later, the surviving Avengers discovered a way to travel through time. They went back to obtain the Infinity Stones from different points in history.

In Endgame, Hulk used the Stones to bring everyone who disappeared back.

But there was a major problem: the Thanos from the past eventually discovered what the Avengers were doing and traveled to the future with his army.

That led to the huge final battle.

Eventually, Tony Stark/Iron Man obtained the Infinity Stones and snapped his own fingers, using their power to destroy Thanos and his army. The power of the Stones was too much for Tony's human body, and he died.

So the basic story is:

Thanos' belief → collect 6 Stones → Snap → half of life disappears → Avengers survive for 5 years → time travel → recover Stones → Hulk reverses the Snap → Thanos attacks → Tony Stark uses the Stones → Thanos is defeated.