An electronic signature, or e-signature, is any electronic means that indicates either that a person adopts the contents of an electronic message, or more broadly that the person who claims to have written a message is the one who wrote it (and that the message received is the one that was sent). By comparison, a signature is a stylized script associated with a person. In commerce and the law, a signature on a document is an indication that the person adopts the intentions recorded in the document. Both are comparable to a seal.
Increasingly, encrypted digital signatures are used in e-commerce and in regulatory filings as digital signatures are more secure than a simple generic electronic signature. The concept itself is not new, with common law jurisdictions having recognized telegraph signatures as far back as the mid-19th century and faxed signatures since the 1980s.
In many countries, including the United States, the European Union and Australia, electronic signatures (when recognised under the law of each jurisdiction) have the same legal consequences as the more traditional forms of executing of documents.
The information on this page is from these sources:
http://www.law.cornell.edu/rules/fre/rules.htm#Rule1001 See US Federal Rules of Evidence 1001, 1002, and 1003