Pastel refers to three things generally.

1) Coloured crayons consisting of pigment with enough aqueous binder to hold it together.

2) the actual art created using pastel crayons

3) the technique of using pastels

Although a beautiful medium favoured by many artists and collectors, Pastel art is problematic to conserve. The powdery pigmentation stays as dust on the surface, and the artwork then gradually deteriorates. However, you can make pastel art last long by applying a fixative spray to add something equivalent to lick of varnish. Also you can preserve the art by keeping it behind glass, though during the framing you must ensure the glass itself doesn’t touch the pastel, but an outer passepartout.