What is inertia and how does it affect the movement of a car?

When I'm running in the morning and I have to brake suddenly, I feel how my body wants to keep going forward, that's inertia, basically. The same thing happens with a car: inertia is the tendency that objects have to maintain their state of motion or rest, so when you accelerate or brake, the car resists that change. That's why it's important to keep your distance when braking and not make very sudden movements, because the car is going to want to keep going in the direction it was going before you change speed or direction. It's one of those physics things you experience every day without even thinking about it.