A corporate action is an event initiated by a company that changes something structural about its shares or distributes something to shareholders — distinct from ordinary day-to-day trading, and reported separately from a company's financial results.
A dividend is a direct cash payment to shareholders, usually expressed per share (for example, ₹5 per share) or, in some Indian disclosures, as a percentage of a share's face value. Dividends are declared by a company's board and paid to whoever holds shares as of a specified record date; not every company pays one, and among those that do, the amount and frequency vary company to company and year to year.
A stock split divides each existing share into a larger number of shares at a proportionally lower face value — a 1:2 split turns one ₹10 face-value share into two ₹5 face-value shares, for instance. A split changes the number of shares outstanding and the price per share proportionally, without changing the total value of what a shareholder holds or anything about the underlying business; splits are typically carried out to bring a high per-share price back into a more commonly traded range.
A bonus issue gives existing shareholders additional shares free of charge, in a fixed ratio to what they already hold — a 1:1 bonus gives one new share for every share already owned. Like a split, a bonus issue increases the number of shares outstanding without shareholders paying anything or the company's underlying value changing; the difference is technical (a bonus issue capitalises reserves into share capital on the balance sheet, where a split simply subdivides existing face value), but the practical effect on a shareholder's holding is similar.
A rights issue offers existing shareholders the opportunity to purchase additional new shares, usually at a discount to the prevailing market price, in proportion to what they already hold. Unlike a bonus issue, a rights issue is optional and requires payment — it's a way for a company to raise fresh capital directly from its existing shareholder base.
Because splits and bonus issues change the number of shares outstanding without changing anything about the business, historical price data needs to be adjusted for them to stay comparable over time — otherwise a split would appear as a sudden, artificial price drop in a chart. This app stores close prices already split- and bonus-adjusted for exactly that reason, so a corporate action in a company's history doesn't show up as a false price movement.