A stock split occurs when one share of the outstanding stock is exchanged for a greater number of shares.
A 2:1 split or a 2 for 1 split exchanges 1 share of stock for 2 shares of stock.
The market capitalization of the company remains constant before and after the split, so if each share was previously priced at 30, they are now priced at 15. So if the total outstanding number of shares is 100 pre-split, then the pre-split market capitalization will be 3,000 (100 shares x 30 = 3,000). The post-split market capitalization remains the same even though there are now 200 shares (200 shares x 15 = $3,000).
A reverse stock split occurs when multiple shares of the outstanding stock are exchanged for a lesser amount of shares. A company would do this to raise the price of its stock.
A 1:2 split or a 1 for 2 split exchanges 2 shares of stock for 1 share of stock.
The market capitalization of the company remains constant before and after the split, so if each share was previously priced at 15, they are now priced at 30. So if the total outstanding number of shares is 100 pre-split, then the pre-split market capitalization will be 1,500 (100 shares x 15 = 1,500). The post-split market capitalization remains the same even though there are now 50 shares (50 shares x 30 = $1,500).