Some tour operators try to cash in on the appeal of ecotourism by using the word without necessarily offering the important components of an ecotour. Companies simply pick up on the word, which sounds trendy and good, and use it in their marketing. There's no global standard for use of the term, though some organizations have tried to set up such much-needed standards. Travelers get a chance to participate in some effort to preserve the natural environment and interact with local people.
Soft adventure is a less strenuous form of adventure travel.
The two terms aren't necessarily related, though soft adventure travel can be part of an ecotourism trip. Examples of soft adventure are staying with primitive tribes in northern Thailand, observing sea turtles on Costa Rican beaches, scouting polar bears in northern Canada, etc. One may hike, bike, white-water raft or simply watch wildlife, all the while staying in hotels and camps with special amenities. Soft adventure, in effect, is really striking a bargain between serious adventure and more traditional packages. It can be for anyone who likes the outdoors or who wants to see rural life, not just the familiar big city tourist destinations.