Hybrid publishers are an emerging breed of experienced publishers who are an alternative to traditional publishing or self-publishing.
Traditional publishing generally requires having an agent; and both agents and traditional publishing houses are extremely hard to break into because they select very few of the manuscripts submitted to them, especially if they are written by first-time authors. Self-publishing requires learning a whole new set of skills including formatting, editing, cover design, promotion and distribution and fulfillment. You may be able to do some of these things yourself, but the quality is not likely to be there unless you hire people for the different aspects. Plus, you will find that retailers and libraries will not purchase self-published books.
A hybrid publisher works with writers to create a professionally edited, produced and attractive book that will be promoted and distributed to the worldwide book trade. The relationship between a hybrid publisher and an author is much closer and personal than in either traditional publishing or self-publishing. Like a traditional publisher, a hybrid publisher carefully vets the manuscripts it accepts for publication (unlike a self-publishing operation which publishes anything submitted regardless of content or quality). The likelihood of a first book being highly successful is extremely slim, so the author and the hybrid publisher share the risk; the publisher provides the same quality services of a traditional publisher and the author pays a fee for those services. In the end, the author has a book that he/she can be very proud of and that will be promoted globally. In many cases, a book produced in this way can be a stepping stone to increased recognition from the larger traditional publishing houses.