A very generic question
It is very hard to answer this question because it is very generic.
In order to get a clearer answer you'd have to narrow down your definition of what exactly constitutes subliminal message and what exactly constitutes an effect.
Once done, you can now talk about specific types of stimuli processed purely by the subconscious, and ...
A target is:
A stimulus that a research participant or subject is searching for or
trying to concentrate on, and that in research is often accompanied by
And a foil is:
In research methodology, another name for a distractor.
For example, in a multiple choice question, the correct answer is the "target", and the rest are "foils" or ...
Often, experimental designs in psychology contain a target participant (who receives the experimental manipulation) and then also other types, such as:
control: no intervention, or a different intervention
confederate: fake participant (actor, or often research assistant)
observer: in social influence paradigms
perhaps foil is a confederate. Hard to know ...