Here's why:
* "Je t'aime" literally translates to "I love you," but it's commonly used as a way to express deep affection and longing, including missing someone.
* "Tu me manques" translates to "You are missing to me" and is another way to say "I miss you" but it's less common than "Je t'aime."
The best way to say "I miss you" depends on the context and your relationship with the person you're talking to.