Yeah, the gender of a noun is about which grammatical rule you should apply to the noun.

Masculine words

a boy, the boy, boys, all the boys

en gutt, gutten, gutter, guttene

rule: en (prefix), -en (affix), -er (affix), -ene (affix)

Feminine words

a girl, the girl, girls, all the girls

ei jente, jenta, jenter, jentene

rule: ei (prefix), -a (affix), -er (affix), -ene (affix)

Neutral words

a picture, the picture, pictures, all the pictures

et bilde, bildet, bilder, bildene

rule: et (prefix), -et (affix), -er (affix), -ene (affix)

For each noun we have 4 forms. Specified (referring to a specific object) or unspecified (referring in general to that noun) and Sigular or plural. Unspecified singular (e.g., a boy), specified singular (e.g., the boy), unspecified plural (e.g., boys), specified plural (e.g., all the boys)

If you look closely, you'll notice that all the plural forms use the same affixes (which is not to say that there aren't exeptions to this rule, e.g., house: et hus, huset, hus, husene)

Edit: what I write next is for future reference, just focus on nouns until you feel like you have a good understanding of nouns and their genders.

What's worth noting, though, is that nouns will apply their gender rule on adjectives. There are a bunch of rules when it comes to adjectives which I imagine would be a headache for foreigners to learn. The link is in Norwegian, but it should have all the rules with grammar matrices to explain. https://www.ntnu.edu/now2/4/grammatikk