Question

What do you mean by "electron is a wave packet"? What is meant by "wave packet is a localised wave"?

Answer 1

According to the wave theory of matter and radiation an electrons can considered to be a wave packet. This means that an electron is not a particle, like we intuitively assume to be, but a collection of small wavelets of close frequencies (like beats). A collection of these small wavelets is termed 'wave packet'.

A wave packet is a wave of short duration or burst and is thus said to be localized or present in a given vicinity.