Krdytkyu

...but where do you go to learn what is under the hood

Trying to understand the operating system is unfortunately not as easy as just opening the bonnet

So it seems like hood is equivalent to bonnet...? But what's the difference? Is that opening the bonnet has other usage?

The cover of a car's engine is called a bonnet in British English, and a hood in American English. Also, at the back of a traditional car design, the luggage compartment is called the boot in BrE, and the trunk in AmE.

In addition to the basic "Americans use hood and Brits use bonnet but it's the same thing", you can look at the origins for the term and see that they both also describe very similar pieces of headgear:

A hood is a cold weather cover for your head...usually nowadays we would say it is attached to a jacket or coat, but it used to be more common for it to be a completely separate piece of clothing. It covers the back of your head completely and usually comes forward a little bit, shielding the face without covering it.

A bonnet is an old fashioned type of hat that women used to wear, which covers the back of the head and usually comes forward, shielding the face without covering it.

In old fashioned cars, the shape of the hood/bonnet actually slightly resembled a hood/bonnet (clothing). So it's no surprise that people picked those words to describe it.

The hood is the term used for the hinged opening to a cars engine compartment in American English.

Bonnet is the term for the same thing in Britsh English, so you will see both used depending on where the writer of the article comes from.

In order to check the condition of a car particularly a second hand one before buying it, it is considered important to open up this engine compartment to check the state of the components there.

They are both used as metaphors for understanding how things work such as computers and other devices.