The intention in the original engram or incident is to implant an idea or emotion or sensation, regarding some person, place, or thing, etc. The intention in Scientology and Dianetics is to erase the compulsive or command effect of the idea, emotion, sensation, etc. so that the person can make a rational judgment and decision in the affected areas of life.
Scientology practices often have to do with addressing implants taking place prior to the current lifetime — one of the most notable is the large R6 implant, said to have been placed in the human mind 75,000,000 years ago by Xenu — but in some cases current life implants are addressed. Examples of implants according to Scientology include Aversion therapy, Electroconvulsive therapy, hypnosis, various attempts at brainwashing, and the inducing of fear and/or terror. Note that this is not a complete list, as many kinds of incidents can include implants as an element.
Other important implants in Scientology doctrine include the Helatrobus implants, which Hubbard claimed occurred 382 trillion years ago to 52 trillion years ago by an alien nation called the Helatrobans. As the story goes, the Helatrobans were motivated by a fear of free thetans and sought to restrain them by capturing and brainwashing thetans in order to weaken them. These implants are said to linger in the subconscious minds of humans today, and are said to be responsible for the concept of Heaven.