The term "treesomes" is a combination of two words: "threesome" and "tress". In the context of adult content, it refers to a sexual scenario involving three individuals engaging in sexual activities with each other. However, there might be some confusion due to the usage of the word "trees", which usually means large plants with woody stems.
In this case, it is likely that the creator intended to use the term "threesome" but made a typographical error or used a creative spelling. It is not a widely recognized term and might cause confusion among English speakers. It would be more accurate to say "threesome" instead of "treesomes".