Google Bard is still under development (which is made clear when you sign up for an account and start using Google Bard) and, as such, its knowledge base is incomplete. This is largely the reason why Bard occasionally makes a mistake and produces inaccurate responses.
As a conversational AI, Google Bard is trained on an enormous amount of text-based data to provide human-like responses to prompts and questions. However, Bard can’t always distinguish between fact and fiction, and not all the data it pulls from the internet is accurate or up-to-date.
When Bard gets a question wrong, you are encouraged to report the mistake, and can even correct Bard by providing it with links to accurate or correct data. Bard continues to learn as it obtains more data, and Google is working to improve its overall accuracy to make sure it isn’t used to spread misinformation.