In Diablo 4, aspects are powerful passive abilities that can be added to your gear. They can be extracted from legendary gear, and then imprinted on other gear to give it a new aspect.
To extract an aspect, you will need to visit the Occultist in any major town. He will be able to extract the aspect from any legendary item, but it will destroy the item in the process.
Once you have extracted an aspect, you can imprint it on any other piece of gear. To do this, simply visit the Occultist again and select the aspect you want to imprint. He will then imprint the aspect onto the gear, and it will be permanently added to the item.
Aspects can be a great way to improve your gear and give you a boost in power. By extracting and imprinting aspects, you can get the most out of your legendary items.