There are several differences between public companies and private ones. For one, as many mentioned, a public company is able to sell shares of the company to the public, while private companies cannot (however they can sell private shares to investors). Another one, which I found interesting, is that public companies must report their records to the SEC while private ones do not, provided that they are under 10 million dollars and under 500 shareholders. This means that the SEC does not have as much regulatory control over private companies! Yet another difference is the main source of funds for the two: for public companies, it’s from selling shares and bonds and for private companies, it is from investors/venture capitalists.
Each definitely have their own pros and cons, but for public companies, their biggest pro is getting a great deal of capital to invest into the company. The biggest con might be the regulations that public companies have to abide by. For private companies, the biggest pro is the limitation of risk, since there is much more control in investors and money flow. The biggest con might be the lack of liquid funds to invest in ventures or in the company.
One example of a company that was once private but is now public is Spotify, who set their IPO back on April 3rd. By going with their IPO, they rose to 26 billion dollars, immensely growing the company, showing how successful it was.