This page explains all the aspects of the AAGRINDER terrain generator which don't require technical knowledge to be understood. For a more in-depth explanation, see AAGRINDER terrain generation (deep).
A world seed is a number which determines the generated world. Whenever random numbers are generated, they are based on the world seed. Because of this, generating two worlds with the same seed will result in two identical worlds. The world seed should be specified in the server settings. Alternatively, if using the CLI terrain generator directly, the world seed is specified as the last argument.