To be more specific, human fusion experiments tend to run at roughly ten times the absolute (kelvin) temperature at the heart of the Sun, which notoriously is its hottest part. (The surface of the Sun is a chilly 6000K, barely enough to keep one's feet warm.)

It initially seems counterintuitive that our smaller experiments need much higher temperatures, but the basic idea behind fusion is to push hydrogen nuclei close enough together so that a few of them fuse into helium.

In the center of the Sun, a hydrogen nucleus can travel of thousands of kilometers before fusing, so the pressures need to be a lot less.

This is also why the average power output of the Sun by volume is so low - less than 300W per cubic meter, less than the human body.

To make a self-sustaining fusion reaction on Earth, we need orders of magnitude more power per cubic meter, and thus the high temperatures!