HD

"HD" is the name of the current most advanced coatings available for Pentax lenses. Building on the famous SMC coatings, it improves contrast and flare management.

DA

"DA" refers to a lens designed for APS-C cameras.  The lens carries information used for specific program lines, in-camera lens corrections, and so forth.

F

"F" is the maximum aperture of the lens, 2.8 in this case.

ED

"ED" means that the lens uses extra low dispersion elements to improve optical performances.

PLM

"PLM" means Pulse Linear Motor. It is the most recent AF engine from the company, and is near-silent and substantially faster than the older screw-drive design.

"AW" means the the lens is weather resistant and can be used in "all weather". It cannot be submerged but will resist splashes, rain, snow, dust and other adverse conditions. AW is superior to WR; since this lens both zooms and focuses internally, a high degree of water resistance is expected.

"SP" is not part of the lens name, but still an important part of its characteristics. Super Protect is a type of coating used by Pentax that helps repel dust and grease on the front element, making the lens easier to clean.