It is a gender of a noun. In English nouns have no gender, but in most other languages, such as Norwegian, nouns do have gender. And there are feminine, masculine and neuter gender.
In English you always use 'a/an' for the indefinite article, and always 'the' for the definite article. But in Norwegian, there are 3 possibilites for the indefinite, and 3 for the definite article -- dependable on the gender.
Also, at some other occasion you'd need to know which gender is a noun to stay correct -- such as with possesive pronouns, making plural etc.
Sometimes, but in most cases you just have to learn the gender with the noun.
Nouns ending in -sjon, -het, -else and -dom in their base form are masculine.
Nouns ending in -em, -um, -gram, -tek and -eri are mostly neuter.
Nouns ending in -ing (when based on verbs) and -inne are feminine.
If you know the definite singular ending of the noun, you can use that to find the gender:
-en = masculine or feminine
-a = feminine
-et = neuter
No, I can think of more masculine than neuter ones off the top of my head.
What I can say - and this doesn't pertain to English in particular - is that very few loanwords are feminine. However, that just narrows it down to the two most common genders, so it's of limited help.