Resistance is the property of resistors by which it opposes the flow of current through it. Many types of resistors such as carbon, metal film etc don’t contain values of resistance imprinted over them. Instead, they use color bands over them.
Today Electrical Engineering XYZ shares the 4 Band Resistor Color coding chart which helps you calculate the resistance by identifying their colors.
You can also use this color coding calculator to find the value of resistors.