Collaboration is a tricky concept. (see wikipedia link above) Collaboration in corporations and in IT are well understood. Collaboration within the arts is a bit more ambiguous. A movie or theatre production, symphany, or any of the performing arts utilize collaboration every step of the way. For a visual artist, working in isolation in the studio, collaboration is more difficult to achieve. Outsourcing, a form of collaboration, is one way of working with others. If I design a product (an artwork) and don't want produce it myself, I have to find an external studio or factory to produce my design. The work of realizing a product in production can become a form of collaboration at this point because getting it right takes back and forth. Samples are made and approved, or changes must be specified. This isn't really collaborating, though. The producer doesn't have any creative input into the design itself, unless the author is open to the craftsmen's ideas, creatively.
Working with another artist or designer and collaborating directly on the development of a product or idea can be very hard for the independent often egocentric artist. A mature artist has a stake in their style, in their identifiable voice. Partnering with another shifts the purity of that voice. Suddenly, 2 voices are speaking in unison or in harmony or not. Picasso and George Braque invented cubism together. This was collaboration and changed art forever.
Process is where the art happens. When the process creates a product, it becomes something else. Then the art becomes selling the work, if you can wrap your mind around that. Continuing to be in the creative processs, with another, working through egoic insecurity, developing work that goes beyond both artists, that is succesful collaboration. Not easy to achieve.