About electrical resistance
Resistance measures how strongly a component opposes electric current. One ohm is the resistance that lets one ampere flow when one volt is applied (R = V ÷ I).
Resistor values span a huge range, so prefixes are used: a pull-up resistor might be 10 kΩ (10,000 Ω), an insulation test reading might be hundreds of megohms, and a cable or contact resistance is measured in milliohms.
On circuit diagrams the letter often replaces the decimal point: 4k7 means 4.7 kΩ and 2M2 means 2.2 MΩ.