Violation without justification or excuse of one or more of the exclusive rights in a work granted by copyright law.
For example, if a copy of a book, song, or computer program is made, or a song or play performed without permission, the copyright in that work has been infringed. What sort of infringement has taken place depends on the level of knowledge and involvement of the infringer.
Direct
Direct infringement takes place when a person who is not the rightsholder performs or engages in one of the activities that the copyright holder has the exclusive right to perform.
Direct infringment is the most common kind of infringement, and takes place whenever a user violates any of the rights granted to a copyright holder.
“A plaintiff must meet two requirements to establish a prima facie case of copyright infringement: (1) ownership of the allegedly infringed material and (2) violation by the alleged infringer of at least one of the exclusive rights granted to copyright holders.” -- LGS Architects, Inc. v. Concordia Homes of Nev., 434 F.3d 1150, 1156 (9th Cir. 1996)
For example, if a copy has been made without permission, that is direct infringement.
Indirect /secondary
These are two types of of infringement that take place in conjunction with direct infringement.
NOTE: There can be no indirect or secondary infringement without a concurrent act of direct infringement. An act qualifies as a particular type of infringement according to the knowledge, intent and abilities of the infringer.
Contributory
A contributory infringer has knowledge of the related direct infringement, i.e. that it is taking place; and must make a material contribution to it in some way.
Examples of contributory infringement would be a CD factory owner who knows that his machines are being used to make illegal copies of protected works, or someone who provides software tools for cracking encryption regimes.
Vicarious
A vicarious infringer is one who, while not deliberately encouraging or materially contributing to the direct infringement, has the right and ability to control or prevent infringement, and benefits from it, even if he or she does not realize the infringement is taking place.
Vicarious infringment is roughly akin to “you should have known infringement was taking place, and done something about it.
A club owner who hires performers who then play protected works without permission to do so, and without the owner’s knowledge, is vicariously infringing. The owner herself is not infringing, or helping the performer to do so, but she could make sure of the performer’s licensing, and she is indirectly profiting from the infringement, because of the revenues from patrons of the club. Another example would be someone who runs an outdoor market, renting stalls to vendors. If a particular vendor is selling infringing goods, the market owner is vicariously infringing. (For a classic example in US law, see Fonovisa Inc. v. Cherry Auction, Inc., 847 F.Supp. 1492 (E.D. Cal. 1994).
Inducement
The idea that someone might not only make the means of infringement possible, but might encourage others to infringe, even if the inducer is not profiting, either directly or indirectly.
Inducement was perhaps made most famous by the US case M.G.M. v Grokster. In the Grokster case, the court found Grokster liable for indirect infringement, because it had actively induced others to directly infringed, regardless of any substantial non-infringing use of the Grokster technology. This was in contrast to the Sony v Betamax decision in the 1080’s which found video recorders non-infringing because they could be used in non-infringing ways, and because Sony had not encouraged infringing uses.