Pockets
The trader buys bitcoins automatically at a suitable buy moment. To spread the risk, it buys bitcoins for a limited percentage of the available euro or USD budget. This percentage depends on the market. For more explanation, see the blog post on the Improved trading engine.
The trader can pick a good buy moment fairly accurately, but it cannot see the future. That is why it does not convert the whole euro or USD budget into bitcoins at once: a more interesting buy moment may follow.
Every purchase of bitcoins is stored in a pocket. On the pockets page you get an overview of all unsold pockets. You can see how many bitcoins are in each pocket (amount), the price of the bitcoins, and how much was paid for the pocket in total. You can also see the fee paid to the exchange for the purchase. The fee is typically 0.25% of the value of the pocket. The age column shows how long ago the pocket was bought.