In short
Peptide therapy is the use of short chains of amino acids (shorter than a full protein) as therapeutic agents, designed to mimic or modulate the activity of naturally occurring signaling peptides in the body.
Peptides act as hormones, growth factors, or signaling molecules throughout the body, and the therapeutic category ranges enormously in regulatory status and evidence quality — from FDA-approved drugs that happen to be peptides (like insulin and GLP-1 receptor agonists) to compounds sold by research-chemical suppliers with no approved human indication, no standardized manufacturing oversight, and only preclinical or anecdotal support.
Between those extremes sit peptides like BPC-157 and GHK-Cu, which have real preclinical (animal and in-vitro) data suggesting tissue-repair or wound-healing mechanisms, but limited or no completed human clinical trials for the indications they are marketed for, and no FDA approval for general therapeutic use — BPC-157 in particular has been placed on the FDA's do-not-compound list for human use in the U.S., which restricts how compounding pharmacies can legally provide it.
Because "peptide therapy" covers such a wide range of individual compounds, evidence quality has to be assessed peptide by peptide rather than assumed for the category as a whole — this is precisely why this site grades each peptide on its own evidence page rather than making a blanket claim about the category's safety or efficacy.