One language - Two variations

When I first came to America and met American jews, I was fascinated to learn that the Hebrew they are familiar with is very different than the Hebrew I'm used to speak and hear on a daily basis from back home, which is Israel.
I noticed that when talking to a jewish guy living on my dorm room floor. Even though he is fluent in Hebrew, he couldn't understand many of the words I was saying when talking to my parents over the phone in a casual conversation. He was very confused because many words sound like other words as they come from the same root, but the meaning is completely different.
The reason that American jews can’t fully understand the “Israeli” Hebrew is because there are two different variations of the same language. American jews know biblical
Hebrew from the bible. And that was the only form of Hebrew until the 19th century. Until the 19th century Hebrew was considered a dead language for over 3000 years (it wasn’t the first spoken language to anyone), and the only use to the language was for literature and prayer.

What changed in the 19th century? Eliezer Ben Yehuda and the first Aliyah (in loose translation- going up to Israel, which means Jewish people from around the world that move to live in Israel). Eliezer Ben Yehuda is considered the resurrector of the Hebrew language, as he transformed the language from an ancient language into its modern
form, which has been Israel’s official language since 1948, the national foundation
year. 

In high schools in Israel, it is mandatory to learn bible studies. With this realization that Hebrew have two very different variations I look back to when I was in high
school and I understand why I was having such a hard time understanding the meaning of the words from the bible even though I use words that sound similar on a daily basis.