From foldoc (....doc.ic.ac.uk/.../....cgi?query=framework):

Framework - In object-oriented systems, a set of classes that embodies an
abstract design for solutions to a number of related problems.

A pluggable architecture  is one where implementations of components in the
system can easily be replaced with other implementations as long as they share
the same interface.

a ramework is just a pattern u will folow in your coding, it defines witch
kind of classes u will make and what each will do...
a really recomend u to read abour MVC (Model- View-Controller) frameworks.
There are lots of frameworks  that follow MVC design pattern like RETA
or GROUNDS. reading about them will give  u a nice idea of what is a
framework