If a painting is intended to be sold, especially online, then the artist must be particularly attentive to assure that the work is of the best quality of which they are capable and honestly represented since the potential buyer has nothing more than the small computer image to view and basically trusts that the artist has made the effort to assure the quality of the offered work without equivocation.
Art is an ambiguous term, however painting as an art medium is not and painting intended to be art will be, though it will not always be good art or good painting. Painting, along with other attempts towards artful expression is a thoughtful process whereby shapes, colors and values are composed and rendered striving for an image which will be pleasing, evocative and poetic as would be the case for many media, though painting alone is contingent upon the craft of brushwork, which at best is mindful yet unaffected. Brushwork is the means to an end and not the end in itself. Since there are many subtle choices, most of which are personal and intuitive with regard to any particular brush and how it is manipulated, how paint is mixed and applied there can also be an element of art to the brushwork itself, though always towards the desired goal.