Symbol next to skills

[Kethevin]

Pardon my question if it's obvious somewhere, I'm learning.

I see a small square symbol on the skill page of character sheets, next to the Prof box for Acrobatics, Athletics, Stealth, and Thievery. What does it mean?

[Trenloe]

Armor check penalty. It’s a small breastplate (honest).

[Kethevin]

Armor check penalty. It’s a small breastplate (honest).

That makes sense and I'm sure I would have come to in my reading of the book soon. Sometimes my curiosity gets the better of me.

I do want to say this however, the people on these forums are the friendliest most helpful people I have ever had the pleasure of interacting with. Thank you so much for answering my questions. :-)