Pure honey is considered inherently kosher, and therefore does not require a hechsher (certifying mark).
However, the standards of kashrut (Judaic dietary law) that families follow vary greatly. The strictest people will eat only foods that have reliable Orthodox kosher certification. The certification ensures that all utensils and equipment used to process and store food items meet kosher standards. After all, you would know if you keep a kosher kitchen. Certification ensures the third party has also met those same standards. The hechsher of the certifying rabbinical court is placed upon the product to demonstrate that the item is kosher.