Yes, a stealth startup is a real company. A startup that is in "stealth mode" is a company that is working on a new product or service that has not yet been publicly announced. The company is usually keeping its work secret in order to generate buzz and interest when it does eventually launch.
There are a few reasons why a company might choose to operate in stealth mode. First, it may be trying to avoid competition. By keeping its work a secret, the company can avoid having other companies copy its ideas. Second, a stealth startup may be trying to build up hype for its product. By not revealing what it's working on, the company can generate buzz and interest that will help it succeed when it does launch.
Of course, there are also some drawbacks to operating in stealth mode. First, it can be difficult to attract investment capital when investors don't know what the company is working on. Second, it can be difficult to attract top talent when potential employees don't know what the company is doing.
So, overall, a stealth startup is a real company that is working on a new product or service that has not yet been publicly announced. There are both advantages and disadvantages to operating in stealth mode, but ultimately it is up to the company to decide what is right for them.