Uniform acceleration means acceleration is uniform. This means acceleration of body doesn't change in direction or magnitude , for the body in given time.
In uniform acceleration , acceleration is constant, and its direction is same too.
So, when uniform acceleration is applied, body moves in straight path, with increasing or decreasing velocity.
Uniform velocity means velocity is uniform in both magnitude and direction.
Here, acceleration = 0.
For uniform velocity, always acceleration is zero.
The velocity of body doesn't change in magnitude or direction for entire time.
The velocity is constant, and body moves in straight path.