Clip parameters like position, opacity, title fx state and so forth are animatable over time.
The parameters of frames between two so-called keyframes are computed linearly (linear interpolation). Move the playhead slider in the timeline to specify a point in time and press the plus button in the 'Inspector' to add a keyframe. To set an animatable parameter for a certain keyframe, choose the keyframe from the popup menu (the playhead slider jumps to the keyframe in the timeline) and then set the parameters.
At the bottom right of the 'Monitor' window is the button to enable/disable motion blur; it lets animations appear more realistic. Enabling implies decreased playback performance (and longer export procedures as well).