@Dr_G_Lemaitre (LONG COMMENT SPLIT IN TWO, SORRY)
Sure! First off, you have to understand that many Japanese terms have a written meaning, but also a cultural one - meaning that a word could mean something nice, but actually be an insult, and vice versa - or it could mean something entirely different.
One of the most classic and obvious examples of this would be:
月が綺麗ですね | tsuki ga kirei desu ne (The moon is beautiful, isn’t it?)
When you see this sentence you think "well, yeah, so what?"
What the sentence actually means, culturally, is that someone just confessed their love to you. It's literally a way of telling someone "I love you." It's not used often anymore because Japanese people have gotten more open, but it serves as a good example.
Chibi, as a definition, simply means "petite/small/miniature", and the word itself is usually aimed at young creatures (humans, animals, you name it).
But the cultural use of "chibi" is ALWAYS meant to describe something as "petite/small/miniature in a good way". So small in a cute/endearing way. It's a term that is completely removed from sexuality as it only focuses on something being endearing. If you were talking about a person and referring to their body or wanted to bring attention to tiny features (good/bad) - you'd probably use a word like "chiisai" or something similar, as this word.
It's very hard to convey in an understandable manner, but to sum it up: Chibi is usually not controlled in a sentence by other letters/words, meaning it retains its original meaning at all times - chiisai (and other similar words) is often used with conditional modifiers that can determine the tone, mood, subject and focus of it.
Now that we've clarified that - you can safely assume that if one were to use Chibi, or describe something as Chibi, it means that it is small and cute or something along those lines.
Chibi as an art form, or caricature even, is basically an exaggeration of the term itself - you present a being in an exaggerated form.
This form is/was based on features that "cutify" something by simplifying it, and enhancing the areas that can amplify the "endearing/cute" connection that the word has - which is basically the face, as facial features are amazing for when you want to draw attention to certain areas and clearly show emotions or even personality.
You could essentially think of the chibi art form as a way of reducing the importance of other elements of a character in order to amplify the face, and use the face to convey information. Sometimes, perhaps in a stereotypical way as well - stereotypes can be good and bad, but regardless, you can tell that a smirking girl with pigtails is meant to look a bit bratty for example - the face (and hair too) easily convey the intended "minor personality trait".