https://www.chemguide.co.uk/atoms/bonding/electroneg.html

This page explains what electronegativity is, and how and why it varies around the Periodic Table.  It looks at the way that electronegativity differences affect bond type and explains what is meant by polar bonds and polar molecules.

If you are interested in electronegativity in an organic chemistry context, you will find a link at the bottom of this page.