A stock split is a corporate action that increases the number of outstanding shares by a defined ratio while proportionally reducing per-share value. A 10-for-1 split converts each $1 share into ten $0.10 shares, maintaining the same total market capitalization and ownership percentages, used at private startups to increase share counts before significant grants and at public companies historically to manage share price into a target trading range. It is an economically neutral action at the company level but has real practical impact on how the cap table looks, how share grants are sized, and how the stock is perceived by various stakeholders.
The mechanic of a stock split: