What do you mean by significant figures?

(N/A) Significant figures are the meaningful digits in a measured or calculated quantity that are known with certainty,plus one additional digit that is uncertain.
They indicate the precision of an experiment or a calculated value.
For example,if a volume is measured as $15.6 \, mL$,the digits $1$ and $5$ are certain,while the digit $6$ is uncertain.
Therefore,the total number of significant figures in $15.6$ is $3$.