Instant yeast, also known as quick rise or fast-acting yeast, is a type of dry yeast that is particularly popular among bakers due to its ease of use and ability to speed up the rising process in doughs. It is a granular, tan-colored substance that is dormant until it comes into contact with warm liquid, after which it becomes active and ready to cause fermentation.

Being a more potent form of yeast, instant yeast doesn't need to be proofed or dissolved in water prior to usage and can be added directly to the recipe's dry ingredients. It expedites the baking process by making dough rise faster due to higher concentrations of live yeast cells than active dry yeast.

Since its cells are smaller and rehydrate quicker, they start their work sooner, thus leading to shorter fermentation times. It is particularly suitable for bread recipes with high sugar content because unlike other yeasts, it doesn't slow down in the presence of high amounts of sugar.

However, one should remember to decrease the amount used in a recipe if they're substituting other yeasts with instant yeast due to its concentrated nature. It's a popular choice for home bakers and professional pastry chefs alike, especially when time is of the essence. Notably, instant yeast can be interchanged with active dry yeast, with slight adjustments in measurements.

Instant yeast has a shelf life of about a year, but it can last longer if stored properly, ideally in a cool, dry place or in the freezer. Keep in mind that you should never use yeast past its expiration date as it loses its potency and will not provide the desired results.

Instant yeast can typically be found in the baking aisle of a grocery store, near other products like flour, sugar, and other baking essentials. If you can't find it, ask a store employee as it may also be located in a refrigerated section or near the fresh breads.