Worldsheet
In string theory, a worldsheet is a twodimensional manifold which describes the embedding of a string in spacetime.[1] The term was coined by Leonard Susskind around 1967 as a direct generalization of the world line concept for a point particle in special and general relativity.
String theory 

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The type of string, the geometry of the spacetime in which it propagates, and the presence of longrange background fields (such as gauge fields) are encoded in a twodimensional conformal field theory defined on the worldsheet. For example, the bosonic string in 26dimensional Minkowski space has a worldsheet conformal field theory consisting of 26 free scalar fields. Meanwhile, a superstring worldsheet theory in 10 dimensions consists of 10 free scalar fields and their fermionic superpartners.
See also
References
 Di Francesco, Philippe; Mathieu, Pierre; Sénéchal, David (1997). Conformal Field Theory. p. 8. doi:10.1007/9781461222569. ISBN 9781461222569.