In simpler terms, it's ultra-pure water with a small amount of preservative added to keep it sterile even after you've punctured the vial's rubber stopper multiple times
Here are the most cited benefits: Increased procollagen synthesis: Abdulghani et al

Rare: may affect up to 1 in 1,000 people Acniform and bullous eruptions (acne-like and blistery skin eruptions) Not known: frequency cannot be estimated from the available data Headache, dizziness Nausea (feeling sick), vomiting, diarrhoea Malaise (feeling unwell) Rash, itching Injection site reactions including injection site pain, injection site erythema, injection site pruritus, injection site induration, and injection site swelling (Reactions at the site of the injection) Exanthema (a widespread skin rash) Chromaturia (unusual coloured urine) Fever Hot flushes (a feeling of intense heat with sweating and rapid heartbeat) Chills (feeling of coldness accompanied by shivering) Paraesthesia (feeling of pins and needles) Tremor (tremble or shakes) Hypokalaemia (decreased potassium levels in the blood) Reactive thrombocytosis (body produces too many platelets) Reporting of side effects If you get any side effects, talk to your doctor, pharmacist or nurse
Gastrointestinal research
Injections are often medically necessary for people with Crohns disease, Celiac disease, or those who have undergone bariatric surgery
It also helps make red blood cells and DNA