Question

what is the difference b/w nucleophicity and basicity

Answer 1

In Basicity: nucleophile attacks hydrogen
&
In Nucleophilicity: nucleophile attacks any atom other than hydrogen.

Answer 2

Nucleophilicity (In the context of organic chemistry): Ability of a group with a lone pair of electrons to push another such group out of a carbon centre.

Basicity: Ability of a group to combine with a proton (Bronsted).
Ability of a group to donate a lone pair (Lewis).