Great info from the Vancouver Master Gardeners:
What are some of the differences between traditional bark mulch and arborist wood chips? 
Bark mulch is a waste product of the logging and lumber industries. It is the protective outer layer of tissue on the outside of the trunk of softwood trees (in the PNW this commonly includes cedar, hemlock or fir). Bark is made of nonfunctioning phloem and cork and includes a form of lignin which allows it to store or accumulate compounds such as waxes, oils and toxins, which helps protect the tree against harmful insects, fungi, and microorganisms.
Arborist wood chips on the other hand contain more diverse source materials. Most often they are the living branches of hardwood trees of various species that have been recently pruned. The trimmed branches are chipped by a woodchipper at the job site into small chunks of wood (with active xylem and phloem) and includes any green leaves (or needles if some softwood has been chipped too).
In agricultural or market garden contexts, another term that may be familiar is ramial chipped wood. For an introduction to ramial chipped wood, please see here:
https://huwsgarden.com/blogs/blog/ramial-chipped-wood
Bark mulch can be used effectively in the right context, but be aware that FIRESMARTBC does not recommend use as mulch. From a plant and soil health, not to mention the 
flammability perspective, relative to wood chips, conifer bark mulch adds very little in the way of nutrients.
Wood chips are not only food for fungi, but because of their more complex nature they stimulate a much wider diversity of soil microorganisms and with the slow and steady process of decomposition, can offer a source of fertility that can last up to several years.
Pictured are arborist wood chips used to mulch perennial beds and create paths.
VMG Saylor B & 
Heather N
From the Facebook Post here: