To you as a life insurance consumer, the difference between a stock company or a mutual company really is not much.
The biggest and most important difference to you as the consumer is that you will most likely receive dividends from a mutual company, if your policy is through them, while you will not from a stock company.
There are about 2,000 life insurance companies. Of these 2,000, most of them are stock companies. Usually, the very largest companies are the companies that are the mutual companies, the ones that pay dividends to their policyholders.
Some of these mutual companies have either converted their companies into stock companies or begun the conversion process to turn their companies into stock companies.
However, as a consumer, this should affect you little, unless you are receiving dividends from your company. Otherwise, the difference between stock companies and mutual companies, does little to you or your policy.