What's "look in" mean?

Rebecca

"[On the] outside looking in" is a metaphorical expression about the feeling of being isolated or excluded from society/social groups. You can think of it as that feeling you get when you're looking through a window into a place where other people are, a place where you're not able to/not allowed to enter. This is the idea expressed by the lyrics "all those years outside looking in." Ex: At school, I was often alone. I felt like I was always on the outside, looking in. Ex: Don't just be on the outside, looking in. Challenge yourself to break through the glass.