Basically, the virtual world where migrations take place is constituted by a matrix of demes. Each deme has its own environmental characteristics according to the input files. (Splatche)

Key components of this simulation model include: (i) a three layer intra-deme population structure: hunter-gatherers, non-dairying farmers and dairying farmers. (ii) Population genetic simulation of a LP allele under selection, and an undrifted allele signifying general genetic background. (iii) Intra and inter-deme gene flow and sporadic longer distance migration (following a Gaussian random walk process). (UNIVERSITY COLLEGE LONDON)

The application of the island model is limited because it does not in fact contain explicit geography: migrants are equally likely to have come from any deme in the population. (Oxford Journals)