Delta-8, is an analog of delta-9. What this means, is that chemically it is very similar with one small difference in its structure. Delta-8 contains a bond on the 8th carbon chain, whereas delta-9 bonds with the 9th carbon chain. This creates differences in the two, primarily with the Delta 8 THC being less ready to bind to CB1 receptors (often why people call it THC light).
Delta 8 THC has been observed to soothe sore muscles, promote a sense of better mind body awareness, sensory enhancement, increased giggling or laughing and promote mood lift. Because Delta 8 THC does not readily bind to the CB1 receptor, it is often a favorable option for some, as a cannabinoid that does not create paranoia or psychosis (As Delta 9 THC can in some users).
Delta 8 THC binds to the CB2 receptor as well, which is what is believed to give people the profound therapeutic advantages, without the anxiety or paranoia typically encounter with delta-9 THC.