Click on a row to select it. The row will be highlighted and any previously selected row will be deselected. To select multiple rows, use CTRL+click, which toggles the selection state of a row.
To select a range of adjacent rows, click the first row in the range, and then SHIFT+click on the last row in the range.
Whenever a list window is active, only one of the rows is current. The current row does not have to be selected. The current row is outlined with a slightly wider frame. For some operations, especially while using the keyboard, it is important to know which row is current. Use the Space key to toggle the selection state of the current row.