Resistors with wire leads usually have their value marked as colour coded bands.
The chart below shows examples of 4, 5 & 6 band versions.
Be aware that the third digit is not used when reading the 4 band resistor.
There are also interactive tables available on-line. Here's a couple:
Resistor Colour Code Table And Calculator Decodes 4 band colour codes.
Resistor Colour Code Calculator Shows the colour bands for a given value.
See also Categories: Electronics pages