Delta-8 is a hot-topic these days. This mighty molecule is a cannabinoid. The chemical structure is similar to other cannabinoids found in the cannabis plant. On the other hand, the results provided differ slightly.
Therapeutic Benefits:
Includes increase in appetite, as well as several antiemetic properties. (Antiemetic = Effective against nausea and/or vomiting). It is also known to help treat depression, anxiety and insomnia. Further more, it can help treat pain.
Anecdotally, Delta-8 consumers reported increased energy levels, benefiting both creative and busy professionals.
Legal Status:
This varies by state. It is currently legal in 11 states. However, is it illegal at the Federal level. Most Delta-8 consumer-products are synthesized from the Hemp plant.
Differences between Delta-8 and Delta-9?
Firstly, both come from the Cannabis plant. (Although Delta-8 also comes from Hemp-derived CBD).
Both chemical structures are similar. Technically, they both possess chains of carbon atoms. Both also contain a double-bond. However, the double-bond appears on the 8th carbon atom in Delta-8 vs. the 9th carbon atom in Delta-9. 
In addition, Delta-8 produces less negative effects than Delta-9. That is to say, less panic, anxiety or a dazed state. Some individuals experience adverse reactions from consumption of Delta-9 THC. For this reason, Delta-8 is a preferred therapeutic alternative, producing less psychotropic effects.
Studies:
Research conducted over the past 50 years is promising. More importantly, over 200 peer-reviewed studies show positive results. More research is needed. However, strict enforcement of federal government restrictions/regulations make it hard to legally conduct research. As a result, anecdotal reports help demonstrate the therapeutic benefits of Delta-8.