I am not aware of any particular logic in why a word is feminine or masculine (a stupid answer might be: because in Latin you had feminine, masculine and neutral, the you have the question: why in Latin is a person masculine, feminine or neutral gender ... :-)
The impications of a word being femine or masculine (or neutral) is that articles, adjectives and some forms of verb (ex. participio passato) must "agree" in gender (and number).
Ex.
La mela matura è caduta. (feminine singular)
I fichi maturi sono caduti (masculine plural)
There are exceptions that may surprise the student, sometimes that is due to the word being neuter in latin:
il dito, le dita, il ginocchio le ginocchia
il fucile i fucili
la paralisi, le paralisi
la forbice - le fobici NB meaning changes, they're like two different words