I assume it’s all that in order to make sure your character’s not a mary sue or an unrealistic saint. Every character should have a sin of some sort to make them human, and some kind of weakness that ensures that there’s conflict in the book. If a character can’t be defeated, it’s kind of dull. ¯\_(ﭢ)_/¯
Your characters strengths and weaknesses should mirror each other. For example, someone who has a strength of being very strong willed would have that flipped on it’s head to be stubborn as a weakness. Or someone that is very pragmatic and logical could struggle with empathy and compassion. For my character, Alma, I made his driving personality trait his curiosity. This gives him the strength of being very intelligent because he pursues his curiosity and knowledge, but also very prone to getting in danger because he doesn’t know when to stop and ends up trying to find out things that would be better left unknown.
Yes, personality traits are generally considered strengths and weaknesses, just positive and negative ones. Skills are not the same as strengths and weaknesses in the instance of writing. When people ask about strengths and weaknesses in your characters, they generally mean negative and positive personality traits.