Articles are confusing because it’s not always necessary to use an article in English. Sometimes it’s easier to remember when NOT to use something instead of trying to memorize when to use something... so let´s start with those situations in which you don’t need to use "the":
1. Things in general
Cats are great pets!(You’re not talking about one specific cat or one specific pet. You’re talking about all cats and all pets in general.)
I love reading books.
Houses are expensive in that neighbourhood.
Americans drive big cars.
Use non-count nouns: I love listening to music. (You enjoy music in general, not any specific song or kind of music.)
She’s afraid of heights, so we couldn’t go to the top of the Eiffel Tower.
I love chocolate!
Have you eaten lunch yet?
She’s a vegetarian. She doesn’t eat meat.
Names of holidays, countries, companies, languages, etc. are all proper nouns.
I got a beautiful new dress for Christmas.
I got my mom a necklace for Mother’s Day.
I live in Canada.
I’m going to Europe next month on vacation.
I use Twitter and Facebook every day.
Bill Gates founded Microsoft.
Her son graduated from Harvard.
She goes to Oxford.
I am studying Russian.
I speak French.
3. Places, locations, streets
I left my book at home.
I have to go to work early tomorrow.
NOTE: You don’t need an article for subjects you study at school: Maths, Geography, History, Science.
Places where you DO need to use an article:
I need to go to the bank.
Let’s go to the movies.
My dad is in the hospital.
She works at the post office.
What time do you have to be at the airport?
Please drop me off at the bus stop.
She doesn’t like to go to the doctor or the dentist.
4. Sports and other physical activities :
I love to go skiing in the winter.
I play football every day after school.
5. Noun + number
The train to Paris leaves from platform 2.
My English class is in room 6 on the first floor.
An acronym is an abbreviation (a short form) of a name. It uses the first letter of each word to form a new word.
a. If the acronym is pronounced as a word, don’t use the.
NATO ambassadors met to discuss the situation..
UNESCO is the acronym used for the United Nations Educational, Scientific and Cultural Organization. (UNESCO is pronounced as one word, /ju’nɛskoʊ/.)
You need to use the before acronyms when the letters arepronounced individually, not as a word.
The UN was created after the Second World War.
Other acronyms that need the: The EU, The US, The CIA, The FBI
b. The is not used before university acronyms:
John Smith got his MBA at UCLA.
She has a Ph.D. from MIT.