What are called holomorphic blocks for super Yang-Mills theory are roughly the analogue of conformal blocks for 2d conformal field theory (see Beem-Dimofte-Pasquetti 12, section 2.2).
Christopher Beem, Tudor Dimofte, Sara Pasquetti, Holomorphic Blocks in Three Dimensions (arXiv:1211.1986)
Fabrizio Nieri, Sara Pasquetti, Factorisation and holomorphic blocks in 4d (arXiv.1507.00261)