Blood pressure is usually expressed in terms of the systolic pressure (maximum during one heart beat) pressure over diastolic pressure (minimum in between two heart beats) and is measured in millimeters of mercury (mmHg), above the surrounding atmospheric pressure (considered to be zero for convenience).
Corrosion on the terminals is due to hydrogen gas being released from the acid in the battery. It mixes with other things in the atmosphere under the hood and produces the corrosion you see on the terminals. Generally, if the corrosion is occurring on the negative terminal, your system is probably undercharging.
Always install the positive cable first, then the negative cable. Always remove the cable from the negative battery terminal first, then the positive. To identify signs of a failing battery, you should inspect your battery case for cracks and bulging. You also should look for corrosion around the battery terminal connections and battery hold-down.