What do these gardening terms mean

Active constituent (ai)	The component in the product that actually does the job.
Systemic	The active constituent enters and moves around in the plant’s sap and water system. This means it can affect pests that attack the plant while it is active within the plant.
Contact	The product works by directly contacting the pest.
Stomach poison	Affects leaf chewers and suckers that ingest plant material.
Registration	The product can be sold for the purpose claimed on the packaging
Withholding period	The time that must pass after application of a pesticide before crops can be harvested
Signal heading	The message above the product name that gives some indication of the toxicity of the product.