The first thing that struck me as wrong with the use of o and a for THE. One letter? I really wanted at least an el or, la. Portuguese Articles (called: definite articles) are actually super-practical. Two immediate and big payoffs: (1) You can use the o and a as it! You can also combine the article with words like em, a and de and say them as one word: contractions (*my post with complete description of how this works).
Things (nouns) are usually preceded by the Portuguese article, the » o, or a:
People & Places
Names of people and places (proper nouns) are almost always preceded by an article: o Brasil, a Sandra.
By "it" we mean either it or, him/her as the examples will illustrate: