First, some corrections:
I heard/learned(either is fine) the word "weeaboo" recently.
Does this mean otaku?
How do people become them?
What do people think about such people in your country?
Now, to answer your question:
A "weeaboo" is a non-Japanese person who is obsessed with Japanese culture, especially anime and manga.They usually believe that they are very knowledgeable of Japanese culture even though their knowledge of Japan usually comes entirely from what they've seen in anime and manga. They are often so obsessed with Japan that they act as if they are Japanese or want to be so. Weeaboos are generally not well liked and are seen as creepy.