A founders' round is an investment round that (a) generates the initial cash needed to get the company started, but more importantly, (b) distributes equity to the founders of the company.

Do not start your company by simply giving stock to the founders; the problem with this is that creates a taxable event for the founders because they have received something of value - specifically a security – , which is taxable, instead of purchasing a security, which establishes a basis for the purchase of the stock, and which is not taxable.

Related Question:

How do I add/edit founders round?

Why do I need a founders round? (blog post)