A more thorough explanation:

Regulation S-K is a rule created by the Securities and Exchange Commission (SEC) that requires companies to disclose important information about their business in registration statements, periodic reports, and other filings. This rule outlines how companies should disclose qualitative information about their business, while Regulation S-X outlines how companies should disclose quantitative information, such as financial statements.

Regulation S-K applies to a wide range of filings, including registration statements for initial public offerings (IPOs), periodic reports, tender offers, and proxy statements. It is most commonly used when drafting a Form S-1, Form 10-K, or Form 8-K.

Regulation S-K is divided into different topics and items, each requiring the company to disclose a description of a different material aspect of their operations. Some of the important provisions include:

• Business: Companies must describe the general development of their business, the location and general character of their property, and any ongoing material legal proceedings.
• Securities of the Registrant: Companies must disclose information about their securities, such as market price and dividends.
• Financial Information: Companies must present select financial data for the last five fiscal years, provide management's discussion and analysis (MD&A) of financial condition and results of operation, and discuss internal controls and procedures to ensure the integrity of financial reporting.
• Management and Certain Security Holders: Companies must disclose information about their directors, executive officers, and control persons, as well as executive compensation and any ownership of or transacting in the company's securities by these individuals. They must also disclose certain corporate governance matters, such as director independence and the composition of committees.
• Registration Statement and Prospectus Provisions: Companies must summarize the prospectus and describe how they plan to use and distribute the proceeds of an offering, if applicable, how they determined the offering price, whether the offering will dilute existing shares, and whether existing security-holders are selling their security in the offerings.

In November 2020, the SEC amended Regulation S-K to shift to a principles-based disclosure regime, allowing companies greater discretion in determining which developments meet the materiality threshold and therefore must be disclosed. The amendments also require companies to describe their human capital resources, describe regulatory compliance with all material government regulations, and disclose material changes to a previously disclosed business strategy. The amendments eliminated the five-year and three-year disclosure timeframes, instead requiring companies to focus on materiality.

When a company files a Form S-1 to go public, they must comply with Regulation S-K by providing information about their business, securities, financial information, management, and registration statement and prospectus provisions. For example, they must describe the general development of their business, provide select financial data for the last five fiscal years, and disclose information about their directors and executive officers.