What type of companies are limited by shares according to the given information?

A company limited by shares is a specific type of company structure where the liability of its shareholders is limited to the amount unpaid on their shares. This means that shareholders are not personally responsible for the debts beyond their investment in the company.

Public companies, which can issue shares to the public and are typically listed on a stock exchange, are generally structured as companies limited by shares. This allows them to raise capital from a wider base of investors through the sale of shares. The characteristics of public companies are closely associated with the concept of limited liability, which is a core feature of companies limited by shares.

While private companies can also be limited by shares, the question specifies "companies" in a broader sense, and public companies are a prominent and specific example within the framework of company law. Non-profit organizations and charitable trusts are distinct entities that do not typically operate on a share capital basis and therefore do not fall under the category of companies limited by shares.