Part of being a parent means being there for your child when it’s time to have the big conversations, from ‘what is death?’ to ‘why does Santa look so much like Grandpa?’ There's a good chance that most of these conversations are at least a little ways away - most babies don’t start to play detective over Santa’s shoe size until they’ve started speaking in complete sentences. Other conversations may need to come a little sooner, though, even if your baby might not be ready to hold up her end of the dialogue very well yet.
Babies are blank canvases, both in that they’re full of innocent wonder as they explore the world around them, and in that they really have no idea what’s expected of them in polite company. This means both that your baby doesn’t mean to embarrass you or make anyone angry when she starts climbing all over the fabric of your college roommate’s nice new couch the same way she might in the living room at home, or start wailing when she loses her temper at the library. She is just curious, or restless, or overwhelmed, and is responding the same way she usually does, regardless of the venue.
Some parents find it’s easier to just make a rule against certain behaviors all of the time, instead of trying to explain to your baby that she can act one way at home, and another way in public. In the end, it’s a question of whether you feel it’s better to start talking about the differences between the way people act at home and in public early, so your baby grows up with the idea and grows into understanding it, or whether you feel it’s better to wait to talk about it until your baby can understand and respond in a meaningful way.
One of the biggest keys to conversations with your baby at this age is consistency - she’s not going to get it right away, but if you’ve patiently talked through the importance of using an indoor voice at the grocery store three, or four, or fifteen times, you may notice it start to make a difference. An important part of toddler-proofing is talking to your child about household dangers and how to avoid them, and dealing with public vs. private behavior falls under a similar category.