Why do you need to know what homeopathy is?
but since you ask:
Homeopathy is the idea that “LIKE CURES LIKE”.
Meaning that if a substance causes a particular symptom, then that same substance in very small diluted amounts will cure a disease that causes the same symptom. Never mind what condition or disease caused the original symptom.
Never mind that the fact that this this substance causes the same symptom is based on only one person having blamed the substance for it. Never mind that the the dilutions used bring the solution to zero so that the “medicine”
is all solvent with no solute. Never mind that they claim that the water used has some sort of memory for the drug it was once introduced to but which it no longer contains. Never mind that the whole idea is based on nothing but somebody woke up one morning and invented the theory. Never mind that the idea that LIKE CURES LIKE is too general to be of any use, and so on.