the simplest way to describe the Olodumare/Orisa thing is diffused monotheism...
Olodumare is the Supreme Being He/She who spreads across the Universe like a mat
the orisa while considered to be "deities" are simply manifestations of Olodumare
Olodumare as made manifest in sweet water is Osun Olodumare as made manifest in epidemic illness and healing is Babaluaiye Olodumare as made manifest in the ocean is Yemoja Olodumare as made manifest in farming is Orisa Oko and Onile
the word Orisa means "select head" meaning that an orisa is the head of a particular thing
for example Sango is the "select head" of the thunderstorm but Oya mixes it up in there, and if it's a hurricane believe that Yemoja and Olokun are up in there too
and you have to be careful of humanizing the orisa...the orisa are forces of nature...the personification of these forces of nature is designed to assist us in recognizing the Ase of the forces of nature as they manifest within ourselves...
essentially...everything that is, was, and shall be is a manifestation of the Most High