John Ternus becomes Apple's CEO on Tuesday.

He replaces Tim Cook, who led the company for 15 years.

During Cook's time, Apple's value grew to $4.6 trillion.

This growth came from the iPhone's popularity.

The change comes as Apple faces pressure in artificial intelligence.

The company has had problems delivering promised AI features.

Earlier this year, it showed new upgrades to Siri.

These upgrades focus on privacy and daily use.

Apple is trying to catch up with its rivals.

Ternus must go beyond his hardware engineering background.

He needs to keep Apple competitive in AI.

He also faces supply chain questions.

He must manage relations with President Donald Trump.

Trump praised Cook publicly on Tuesday.

Ternus worked on products like the Apple Watch, AirPods, and Vision Pro under Cook.

He will lead next week's iPhone launch in Cupertino, California.

Cook is expected to stay on as executive chairman.

He will likely help keep Apple's ties with Trump strong.