E12 is a series of standard resistors. Values are logarithmically spaced to ensure uniform relative steps across decades. E12 has 12 resistor values within each decade. For more resistor values look at E24 series.

E24 is a series of standard resistors. Values are logarithmically spaced to ensure uniform relative steps across decades. E24 has 24 resistor values within each decade. E24 has double the amount of values than E12.

Prefixes are used to describe values from the very small to the very large. Pico, Nano, Micro, Kilo, Mega are some of the prefixes.

SI units are the standardized units. The are the ones for electronics. They are the basic units.

Glossary of commonly used words, abbreviations and terms within electronics with description.

Size codes for resistors and capacitors, used when designing PCB's

Here’s a table of widely used batteries, including their physical size, nominal voltage, and approximate rated capacity

Commonly used references of different components on pcbs and schematics