Formulated in the mid 60's, Osmocote has been available in several formulations/ratios for decades. Each fertilizer prill is coated with resins that allow a "controlled release" of macro/micronutrients. The resin coatings are semi-permeable to moisture but, are also temperature dependent. During cool weather, when most plants have little need for large amounts of fertilizer the release is extremely slow. Several different thicknesses are manufactured thereby permitting different ratios of slow and fast prills to be mixed together. The technology is a bit dated but has been the standard of the nursery/container grown industry for many years. I've used it on outdoor grows several times with excellent results.
Since the release is very gradual, it is ideal for a grower that wants to limit their exposure (and overall "fussiness") to their grow patch. Basically, you can incorporate a small amount of this product in to the native soil on the day of transplanting and forget about fertilization requirements through the rest of your grow. The release of macronutrients is so ponderously slow that there is almost zero risk for fertilizer "burn". Unless of course if one fails to read and follow the label directions. Compared to the incredibly expensive "organic" fertilizers for sale at your local grow shops(complete with trippy, colorful graphics) it is hands down one of the easiest ways to feed your plants cheaply and effectively.