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.
When disconnecting a battery, remove the negative terminal (-) cable first, then the positive (+) cable. When connecting the battery, reverse these steps. Attach the positive terminal first, and the grounded or negative terminal last. Be careful attaching cables to terminal posts to avoid creating sparks.