In real-life physics, acceleration due to gravity will change respect to altitude. Check out the attached image (source: Wikipedia).
However, in high-school physics, acceleration due to gravity is represented by the letter g, which has a value of 9.81 meters per second squared.
This means that an object being dropped straight down will be moving 9.81 meters per second faster than it was 1 second ago. I hope this helps! :)