Gated content is any content that your visitors can access only after providing their information. In most cases, this means a name and email address so you can be added to a further marketing list. Some websites have played with the idea of requiring social media follows or likes in exchange for content, which is a viable, but less a much utilised strategy than one that collect information for direct marketing.
When the situation changes, and a business finds that suddenly its old business models no longer work, the successful ones will innovate and adapt to the situation around it. In many aspects, this is the definition of an innovative business and highlights the skillset of a successful entrepreneur from those that are less successful. When the environment changes, it closes some lucrative avenues that were open to the company, but (if you look hard enough) new ones present themselves.