This page, simply, lists all of your investments, how many shares, the initial share price you bought them at, their current price, and lastly, their current value.
How Stocks Work
Stocks are the way all businesses get their funding - and they're also that investors can get as much money as the storeowners. The share value is always equal to the total value of all items and cash in the store over the number of shares. So, when a business is making profits, their share value goes up. When it is losing money on transactions, the share value goes down.
When you buy stocks of a business, you are contributing to the funds with which that business can buy products and make profits. When you sell stocks of a business, you are taking away from the available funds which that business uses to get more profits.