BANGS is an acronyme for the rules about the place of the adjectives in French (beauty-age-number-goodness-size),
They are similar to the existing rules in English, that you use (often without being aware if you are a native) to decide in which order you'll write your adjectives in a sentence with several ones.
If you are curious, it's a bit off-topic, but see here:
English (no acronym):
There are rules for the placement of adjectives in Latin, but it's not as fixed as in French or English.
For instance, for nationality (Wikipedia):
An adjective can come either before or after a noun, e.g. vir bonus or bonus vir "a good man", although some kinds of adjectives, such as adjectives of nationality (vir Rōmānus "a Roman man") usually follow the noun.
(...) One factor affecting the order is semantic. As a general rule, adjectives which express an inherent property of the noun, such as "gold" in "gold ring", tend to follow [the noun]. [And also when] the adjective is more salient or important than the noun, as "Appian" in "Appian Way" (via Appia), it also tends to follow it.
Adjectives which express a subjective evaluation, such as gravis "serious", on the other hand, usually go before the noun.
Adjectives of size and quantity also usually precede (in 91% of examples in Caesar, 83% in Cicero), as do demonstrative adjectives such as hic "this" and ille "that" (99% in Caesar, 95% in Cicero).
Adjectives where there is a choice between two alternatives, such as "left" or "right", or "preceding" and "following", also tend to go before the noun. However, the opposite order is also found.
So, there are some rules.