With the passage of the Agriculture Improvement Act of 2018, Congress redefined "marijuana" and "hemp" at the federal level. The definition of "marijuana" is now applied only to cannabis plants that have delta-9-THC above a certain level of concentration per dry weight. Cannabis plants with delta-9-THC above this threshold are still federally illegal. All other cannabis plants below this threshold are now defined as "hemp" and are exempt from the federal prohibition of marijuana.

Many startups (legitimate and otherwise) have taken this opportunity to create new products that are very similar to actual marijuana, but altered slightly to meet the new federal definition of "hemp". One of those products is "delta 8" hemp. Delta-8-THC is a psychoactive substance found in cannabis, which typically works together with delta-9-THC and CBD to produce marijuana's intoxicating effects. To make delta-8 hemp, growers overproduce industrial hemp and distill out the delta-8-THC. They then take that distillate and either sell it as vape juice, or spray it on industrial hemp to sell as "delta-8 flower" for customers to smoke like regular marijuana.

as others have said, without the delta-9, the high is kind of weird and flat.