Both can save your life, but one more then the other.
In many training classes, you have probably heard the instructor say "You need to get to cover." If a fight erupts around you, you want to get to cover before returning fire. Standing out in the open is a great way to get yourself shot and the number one rule of a gunfight is not to get shot.
Another piece of advice you might hear is, "Make sure that you are not using just concealment when trying to get away. Make sure it is actual cover." But you think to yourself, isn't concealment what you are using to cover your gun?
So what do both these terms mean? What is the difference between cover and concealment?
Cover is the place you want to be when bullets start to fly because it is anything that will stop said bullets. A concrete wall, a telephone pole, a car's engine block; these are all places where you can hide and know that a bullet will not pass through to you. It can be said that cover hides you from a bullet.
Concealment, however, is not the place you want to be when bullets start to fly. Concealment does not stop bullets. These are things like hollow core wooden doors, wooden fences, car doors. All of these things a bullet will pass through and has the potential to hit you.
All concealment does is hide you from sight. Keep in mind that all cover is concealment, since it hides you from both bullets and from sight, but not all concealment is cover.
So how do you determine what is cover and what is concealment? Sometimes it just comes down to common knowledge. Knowing that, at the mall for example, the main pillars holding the building up make for good cover because they are solid concrete. A stone statue in the lobby may work as well.
Other things like a sheet metal garage door or a garbage can are considered concealment. In an office setting, Sheetrocked walls and fabric cube walls would be concealment. These are things that will not stop the bullets and allow them to pass right through.
As you go about your everyday life, make sure you look around and assess where you would go if a gunfight were to break out. Where are your options for concealment? What are your options for cover?
In competition, the reality of things get stretched a little. A tarp hung up to act as a barrier would normally be considered concealment and therefore not be the place to engage targets from. However, for the purpose of the game, it is considered cover and used to protect yourself from those targets.
Sometimes the terms can get confusing. Just always know that cover will stop bullets from getting to you.