A process by which a food product, traditionally a fruit or vegetable, is submerged in boiling water for a brief, timed interval before being removed. Upon being removed, the food product is rapidly cooled, usually by being submerged in ice water. This process is called shocking. The main reason for the rapid cooling is to stop all cooking processes so as not to alter anything else about the food, such as texture.

Truthfully, altering the texture of a given food is only one of the reasons that a food may be blanched. Another reason is that enzymes in the food may be deactivated, thus altering the flavor. Additionally, blanching can preserve/enhance the flavor, preserve the color, or loosen the skin (such as with tomatoes). Another point to add is that the blanching process is meant to be so brief that the food in question is still considered raw.

As implied in the previous paragraph, part of the reason for blanching food is to prepare it for storing the food via canning or freezing. One downside to blanching, though, is that the food in question almost always has less nutritional content than the untreated version. However, if microbes are a concern, blanching does kill microbes on the surface of the food. It also will reduce the amount of pesticides present in the food; however, efficacy of this method varies between vegetables. For a study that goes more in depth on the matter, see here: https://pmc.ncbi.nlm.nih.gov/articles/PMC9141337/ .