the reader gets to know the thoughts of that one character the 1st person POV is in esp bc 1st person POV is narrated with "I" or "we". what they're thinking, how they feel, what they're doing, etc. but what is hidden from the reader is the thoughts/feelings/actions of the other characters.
Explanation:
for example if you're reading a chapter or book that's only narrated in 1st person POV like from the main character, then you're going to get to know that main character the most. everyone else you don't know as well because you're not reading in their POV instead.
