Load cells are used in all applications in which you need to measure a load or force. Everything from weighing a truck (on a weighbridge) to measuring the force required to insert one component into another. Load cells (or force sensors) are very often used in conjunction with LVDT displacement transducers so that the properties of a test object can be measured (i.e. how far it extends for a certain force).
Pressure sensors are devices that convert the pressure of a liquid or gas into an electrical signal. The compressed air line you use to fill up your car tires at the gas station, or the blood pressure monitor your doctor uses, both contain pressure sensors. There are many different types of pressure sensors, but ours use a strain gauge, which measures the deflection of a diaphragm when pressure changes.