In Final Cut Pro for iPad, you can use keyframes to animate:

A clip’s opacity

Transform settings that modify a timeline clip’s spatial properties in the video frame, including the clip’s position, scale, rotation angle, and cropping

Settings of video effects you’ve applied to a timeline clip, such as the amount of blur in a blur effect

Settings of title and object clips you’ve added to the timeline

You add keyframes for specific effect settings in the keyframe editor at the bottom of the timeline, then adjust their values in the inspector. For example, if you want a clip in the timeline to slowly blur into a gauzy haze, you could add the Gaussian blur effect to the clip, then add two keyframes to the effect’s Amount setting—the first with a value of 0, and the second with a value of 1. When you play back the clip, Final Cut Pro interpolates the values between 0 and 1, creating an animated defocus effect.

You can also keyframe volume changes in audio clips.

Note: Transitions can’t be keyframed.