What are neutrons and why are they important to isotopes?
Neutrons are nuclear particles that have about the same mass as a proton, but no charge.
Every nucleus needs these neutrons for preventing these positively charged protons from pushing themselves away from each other (the real story is much more complicated). Usually there are about the same number of protons and neutrons in an atomic nucleus.
Notice the word " about " in the previous sentence.
Carbon, which has 6 protons, usually has also 6 neutrons in its nucleus, but a small proportion of the carbon atoms has 8.
The first is called Carbon-12 and the second Carbon-14, the numbers referring to the total mass number of protons+neutrons.
Both are Carbon, and have the same place in the Periodic System -- that is what 'isotope' means "same place".