DEFINITION

A form of intellectual property that grants authors and artists the exclusive right to the reproduction, derivation, distribution, performance, and display of their original works, including literary, artistic, dramatic and musical works and computer programs.(Source: IPR Helpdesk)

IMPACT ON e-BUSINESS

If you are a content creator, copyright protects your text, image, software etc. from unlawful use by others. You do not need to explicitly make a copyright note for being protected, neither does copyright need registration (as opposed to patents, for example). As the creator, you can decide who can use your work and how it can be used. Exceptions to this exclusive right exist for private copies that are generally  permitted, and some exceptions for non-commercial use.
On the other hand, if you want to use a photo from the Internet, or if you just "bought a software",  you are subject to the same rules, i.e. you need a permission to use the photo (the conditions can be set by the copyright owner), and you can use the software only in the way described in  the licence (you actually almost never "buy" a software but pay for a licence that allows you its use under certain conditions. For more on software licences, see Licensing).

MORE ON COPYRIGHT

Copyright (also called author's right, in the non Anglo-American countries) is very complex and occupies many specialised lawyers, and international organisations such as WIPO (World Intellectual Property Organisation). Digital technologies are a challenge to the traditional  copyright scenario due to the ease of copying (commonly known cases are Kazaa and other music file sharing platforms).
If you have a specific question or concern, you can check out the below links or create a FORUM on this topic.

In July 2008, the European Commission published a Green Paper on copyright in the knowledge economy. This is an important document that tackles new developemnts in content creation, e.g. user generated content. Green Paper text.

PRACTICAL LINKS

Protection of a (business) idea or concept: Ideas are NOT protected. If you confide your million-Euro idea to a business friend, s/he may soon no more be your friend (as s/he can lawfully albeit immorally take up your idea). The IPR helpdesk provides information on how best to protect your IDEA and provides a template for a CONFIDENTIALITY AGREEMENT.

German Urheberrecht and the Internet

WIKIPEDIA article on copyright

RELATED ISSUES

Database protection
Licencing
Open Source Software
Intellectual Property Rights
Digital Rights Management
Hyperlinks