Content marketing is when a business publishes things that don't explicitly try to sell its products or services, and is a critical part of the life of a small business on social media.
At the foundational level, people aren't on social media to be sold to, and if you're not convinced, say "I joined Instagram to be able to look at things I can buy". It feels like a lie. Yes, social media can build a brand and increase revenue, but before all of that, people are on social media because they see it as a way to make connections.
Some of those connections are educational - they want to know more, learn how to do something, or learn how to do something better. Some of those connections are inspirational - they follow people who are operating at a high level of achievement or cruising for the dopamine hit of a well-timed inspirational post. Some of those connections are for entertainment - they want to laugh or be emotionally moved.
While big businesses can propel their marketing with money, for small businesses without a huge advertising budget, content marketing is the only way to successfully exist on social media. It gives people the connection they're looking for.
Whether it's a blog post that teaches me why I shouldn't wear socks with sandals, a Instagram Live video talking about supporting other women who are entrepreneurs, or a funny meme, consistent connection-focused content reaches out to people and says that the business is about more than taking people's money and is willing to be human before it starts trying to sell something.