Kratom powder is generally stronger than crushed leaves because the stem and veins of the leaf are often removed, leaving the parts of the leaf which contain the highest amount of the active alkaloids.
The Stem and Vein is generally removed during the grinding of the leaf to produce powder, but still contains active alkaloids, although only approximately 25% of what the other leaf material contains.
This generally comes in a powder form and is a concentrated form the Kratom, thus providing a stronger or enhanced effect.
The extracted alkaloids or Concentrated Kratom Powder is soluble in alcohol which allows for an alternative delivery system. Tincture droplets are delivered sublingually and have a strong effect.
Enhanced Kratom is often as simple as an extract being added to a regular strength powder. There are also some strains of Kratom that are overall stronger than others and these are sometimes referred to as enhanced.
This is basically what the title implies. Crushed leaf Kratom contains all of the leaf material, stem and veins and is often used as a tea for the delivery system.