What is Speed, Acceleration, and Instantaneous Vectors?
Speed is a scalar quantity of measurement that is defined as the rate at which an object covers a specific distance. This is usually measured as distance over time. In other words, how much distance an object covers over a particular amount of time.
Velocity is a vector quantity. What this means is that the object has not only speed (a magnitude) but also the object has a particular direction. So, this is still a distance covered over time but is now also the rate at which an object changes its position1.
A video resource that helps is here: https://www.youtube.com/watch?v=X4Wxd4m-QVc
Instantaneous speed is the current speed of measure. This is often confused with the average speed. This is not correct. Imagine if a speeding car is tagged at going 105 miles/hour, its speed at measure would be what was recorded. Thus, instantaneous velocity is a snapshot of that object's velocity.
Acceleration is the rate of change in velocity of an object with speed times time. An object’s acceleration is the net result of all of the forces acting on a particular object. The unit of measure is meters per second squared (m/s2). Acceleration due to gravity is the acceleration that an object possesses solely due to the force of gravity acting on it. An object may reach -9.81 m/s^2 * time as it gets close to Earth. This is the objects terminal velocity, but not its maximum velocity. Maximum velocity is theoretical in that objects usually strike the earth before that is reached. Due to air resistance, free-falling objects have a terminal speed that is reached. Remove the resistance, acceleration continues until the maximum velocity is reached 2, 3. Imagine shooting a bullet into space. Its acceleration would be zero, but it would have speed and velocity. It would not have terminal velocity, but it would have maximum velocity.
Each of the above quantities can be changed by gravity and resistance. Resistance can come in the form of wind and water for instance.
When an object is accelerated into motion and the only forces acting upon that object are gravity and resistance, we called this object a projectile4.
References
1. https://www.physicsclassroom.com/class/1DKin/Lesson-1/Speed-and-Velocity
3. https://www.physicsclassroom.com/class/1DKin/Lesson-1/Acceleration
4. https://www.physicsclassroom.com/class/vectors/Lesson-2/What-is-a-Projectile