The Inductive effect is the outcome of Electronegativity; therefore, they are different and not the same.
Electronegativity is an atom or a group of atoms’ ability to pull the electrons in a covalent bond toward themselves. The electron-withdrawal by an electronegative atom causes the electron density of that bond to shift to create two terminals- positive (electron-deficient, δ+) and negative (electron-rich, δ+), classifying the bond as a polar covalent bond.
If the electronegative atom is part of a carbon chain, then the shift in electron density of one bond further induces polarization in the neighboring carbon atoms causing the inductive effect. However, the induced polarisation effect is not observed after four carbon atoms.
The electronegativity scale is relative to Fluorine. Fluorine is assigned the highest electronegativity of 4 and is considered the most electron-withdrawing when part of a two-atom covalent bond. The electron pull by the Fluorine causes an Inductive effect in the neighboring carbon atoms of the chain to which it is attached.
Such electron-withdrawing atoms or groups of atoms show an electron-withdrawing negative inductive (-I) effect. There is also an electron-donating positive inductive (+I) effect.
The electron-donating or withdrawing inductive effect is always measured relative to the Hydrogen atom. For example, Fluoro a -I group will pull the electrons away from itself more than a Hydrogen (H) atom would if it occupies that position in the molecule.
Inductive effect merely compares the impact of an electronegative atom or group with the Hydrogen and the difference in the position of electrons arising due to it, without an actual donation or withdrawal.
The concept helps to understand how the rates of reactions or acidities change in the presence or absence of such groups showing the -I/+I effect.
Related reading: Inductive effect, Electronegativity.