Funding rounds are distinct stages where a startup raises capital from investors by selling equity, moving from early-stage "pre-seed" and "seed" funding to later "Series A, B, C," etc., as the company grows. Each round signifies a significant point in the company's development, attracting different types of investors like business angels and venture capital (VC) firms to provide money in exchange for shares to finance expansion and growth.
A detailed explanation of funding rounds can be found here.