You feel pressure when something presses on you –- whether a physical force or a stressful situation. If you don't crack under the pressure of witnessing the accident, you will calmly apply pressure on the driver's wound until help arrives.
The pressure of a looming deadline might cause you to finally get to work on an assignment. Pressure can also be a verb, like when your friend pressures you to go rock climbing despite your fear of heights. The rocks you would rather not climb were formed long ago by extreme heat and pressure. While climbing, your friend's blood pressure may rise right along with yours when she sees how clumsy you are.