The profit and loss statement shows your incomes and expenses for the given time period. The report includes all transactions starting with the first date and up to and including the ending date.
At the end of the fiscal year, you normally transfer the accumulated profit over to the balance sheet, where it will constitute part of the company equity. In order to still show the profit correctly, the application needs to know the expense account that is used for this purpose so that the account can be excluded from the expense heading and instead included in the bottom line. You can specify which account to use for this purpose under the 'General information' sidebar item.
If you've defined tags in order to group entries by project, et.c., you can select the tag from the middle popup button at the bottom of the view. This will filter out and show only transactions with the given tag.