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In a sigma-model quantum field theory a field configuration is a morphism $\phi : \Sigma \to X$ for $\Sigma$ an $n$-dimensional manifold or similar. One is to think of this as being the trajectory of an $(n-1)$-brane propagating in the target space $X$.
For the case $n = 1$ (for instance the relativistic particle, a 0-brane) the term worldline for $\Sigma$ has a long tradition. Accordingly one calls $\Sigma$ the worldvolume of the given $(n-1)$-brane when $n \gt 1$. For the case $n=2$ (the case of relevance in string theory) one also says worldsheet.
worldline formalism (for scattering amplitudes in QFT)
worldvolume