A keyframe transition controls the camera movement between the current keyframe and the previous keyframe. As you add keyframes to build your animation, you set the interpolation method for the camera between those keyframes by choosing the transition type.
An animation can tell a story without changing how the camera travels but may be more effective at describing a dynamic story when different camera transition types are used. Incorporating a combination of transition types is a useful way to control the narrative of your animation. You can change the transition type in the beginning of the authoring process for your keyframes by setting the Append tool with the desired transition type, or make changes to an already compiled animation by editing the Keyframe List or interacting with the Keyframe Gallery in the Animation Timeline pane.
Camera transition types for new keyframes are set on the Animation tab by opening the Append drop-down list in the Create group. This defines the camera transition when creating each new keyframe.
If you need to create a stationary keyframe in which the camera position does not change, you add a Hold 
transition. This is available for the selected keyframe in the Animation Timeline pane.
You can update an existing keyframe by interactively editing within the Keyframe drop-down list. In the Edit group on the Animation tab, expand the Keyframe drop-down list to view all keyframes and their respective transitions and times.
The Animation Timeline pane and the Animation Properties pane allow for more granular refinement in a more visual format. Connecting the keyframe thumbnail images on the Keyframe Gallery are circular symbols that allow you to click and customize transitions. Additional types are listed if you want to update transitions for the camera as well as for the layer.
Transition types
The following camera transition types are available:
Fixed
A keyframe with a fixed transition creates a gradual and smooth change between itself and the previous keyframe. Fixed, or spline-type, curves can be described as making arcing or S-like shapes over time. For the camera, sequential keyframes with fixed transitions will provide a smooth curvature for the flight path. This is the default transition type for camera navigation.
Adjustable
A keyframe with an adjustable transition creates a path with configurable smooth turns between itself and the previous keyframe. This transition type follows the mathematical logic of a Bezier curve. Control points are used to help define the shape of the curve.
Linear
A keyframe with a linear transition creates a straight line between itself and the previous keyframe. Linear curves are known for making zigzag or Z-like shapes over time. For the camera, sequential keyframes with linear transitions will provide an angular or jagged flight path, which is useful for a straight camera flight such as through city streets. Linear is the default transition type for layer properties. This can be useful for transitioning a layer's visibility state to simulate a fade in or fade out effect.
Hop
A keyframe with a hop transition creates an arc between itself and the previous keyframe. The camera experience along the path is a vertical jump, or bounce, between keyframes. When sequential keyframes are authored with hop transitions, the flight path with vertical arcs is well suited for a tour of key interest locations (for example, hopping from city to city).
Stepped
A keyframe with a stepped transition creates an immediate switch between itself and the previous keyframe. This is commonly referred to as a camera cut. Keyframes with stepped transitions display locations of interest with no flight path between them. Creating a camera cut from one location to the next is like a presentation of slides showing different city downtown areas.
The location of the camera cut between keyframes can be edited using the transition slider. You can choose to cut early or cut late between the keyframes 
in the Animation Properties pane.
Hold
A keyframe with a hold transition will keep the state of the view and all of its keyable properties stationary for the specified hold time (the default is 2 seconds). A hold can be used on any keyframe, and the length of the hold time can be important if you're using it to allow for features to finish rendering, or if there is specific text/labels to read, before moving to the next keyframe location. Insert a hold for the selected keyframe from the Animation Timeline pane. Edit the duration of the hold in the Animation Properties pane.
Ways to modify transitions
Some transition types allow you to adjust how the path is calculated. For example, the height of the hop, or where the camera cut happens during a stepped transition. Turn on the display of the path and keyframes and adjust the perspective of your view especially if working in a scene. On the Animation Properties pane under the Keyframe tab adjust the transition slider for the selected keyframe. For example, if you have four keyframes and you want to adjust the hop height between keyframes three and four, you need select keyframe four. You will see keyframe four, and the path connecting keyframes three and four highlight. Think of it as how it got there instead of where it is going. The hop path will dynamically update its shape in the view as you move the slider.
For a stepped transition, The location of the camera cut between keyframes can also be edited using the transition slider in the Animation Properties pane. You can choose to cut early or cut late between the keyframes.
Use the playback controls to review your edits.