What are the differences between decimal points and significant figures?

The total number of digits to the right of the point are known as 'decimal points' whereas significant figures start from the first non-zero number. Note: As significant figures start from the first non-zero number this could be to the left of the decimal point. We then use the laws of rounding to come up with our final answers!
d.p. = decimal points, s.f. = significant figures

Examples:

a) 704.539018 is 704.53902 (to 5d.p.) and 704.54 (to 5s.f.)

b) 0.0091 is 0.01 (to 2d.p.) but 0.0091 (to 2s.f.)

c) 0.100400 is 0.10040 (to 5d.p.) and also 0.10040 (to 5s.f.) because, from the first significant figure (non-zero) onwards, all numbers are significant. This includes zeros between non-zeros and all trailing zeros.