Full Idea
In standard possible worlds semantics, the semantic value of an expression is an 'intension', a function that assigns an extension to the expression 'at' every possible world. ...It keeps track of the 'modal profiles' of objects, kinds and properties.
Gist of Idea
Possible worlds semantics uses 'intensions' - functions which assign extensions at each world
Source
Laura Schroeter (Two-Dimensional Semantics [2010], 1.1.1)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.3
A Reaction
Personally I just don't buy a semantics which is entirely based on extensions, even if this has sorted out some more obvious problems of extensionality. When I say someone is 'my hero', I don't just mean to pick out a particular person.