Significant figures means the number of digits (figures) in a number that are important (significant).
eg 1 23,568 has 5 significant figures - all of them.
eg 2 23,500 has 3 significant figures - the 2, 3 & 5 - the two 0's are place holders and are not considered 'significant'.
eg 3 0.0045 has 2 significant figures - the 4 & 5 - the 0's before are also place holders and are not considered 'significant'.Â