False friends are words that exist in different languages and while looking similar or even exactly the same, they mean very different things.
Let's look at the German Question Words: “Wer?” and “Wo?” They mean the exact opposite of what they sound like as you will see with the following two examples:
“Wer ist Angela Merkel?” — “Who is Angela Merkel?”
“Wo ist das Brandenburger Tor?” — “Where is the Brandenburg Gate?”
In those examples it’s pretty obvious from context, but if someone asks “Wo ist Brad Pitt?” you’re stuck with just the question stewing in its own juices, and you need to know the question word.
Practice makes perfect!
A good way to practice this is to constantly ask yourself “Wer ist das?” when seeing people and “Wo ist das?” with objects you encounter on your next stroll through the city or when reading a magazine.