The most clear distinction between these two mediums rests in the materials traditionally associated with each. Drawing usually implies working in pencil, pen, charcoal, pastel and even ink. Painting entails the use of a brush, palette knife or sponge and liquid paint.
From a conceptual point of view, drawing provides the foundation for any representational work of art. On the most basic level, it establishes proportional relationships and measures how far objects are from one another. Representational painting uses drawing as its base, building up dimensionality and light and color transitions through paint.
However, it is possible to draw with a brush and paint with pastels or charcoal. Calligraphy and Sumi-e brush paintings are much more akin to drawing in their process and final result. They require the composition of a limited set of lines, usually black, on white paper rather than canvas, that exist in very precise locations in relation to one another and the whole.
Pastel drawings are often indistinguishable from oil paintings if they are rendered with very soft transitions. Charcoal drawings often require building lighter or darker value from an already established "ground" that is not black or white but gray. Likewise, painters rarely begin work on a white canvas, adding and subtracting contours and color values to establish form and distance, as they go along.
Abstract Expressionism and Impressionism tend to remove drawing from painting by prioritizing color fields over contours, but in most other cases artists are drawing with paint or painting by drawing.