Learn Italian: Il cibo è un po' caro. - The food is a bit expensive.

un po' means "a bit" or "a little". The apostrophe shows that the word has been shortened. It is actually short for un poco. Dropping the end makes it faster and more natural to say in conversation!

Can I just use poco instead of un po' in this sentence?

You can, but it completely changes the meaning! un po' means "a little bit", so the food is a bit expensive. If you say Il cibo è poco caro, poco means "not very" or "little" in this context, making it mean "The food is not very expensive."

If I am talking about a feminine noun, does un po' caro change?

Only caro changes. caro is an adjective describing the noun, so for a feminine noun like la pizza, it becomes cara. However, un po' is acting as an adverb here (telling us how expensive it is), so it never changes its ending. You would say La pizza è un po' cara.

Doesn't caro mean "dear"?

Yes, it does! When you are talking about a person or writing a letter, caro means "dear" (like Caro Marco). But when you are talking about things you buy, like food, tickets, or clothes, caro is the standard word for "expensive".