Maxent - the original
Maxent is a freely available open source software used for Species Distribution Modeling (SDM) and Habitat Suitability Modeling (HSM). It is used to predict the habitat of animals and plants on point-based information (presence only data) and information on the environment of the study area. Maxent was created by Steven Phillips and is open source since 2017. You can download the original Maxent here. To get a detailed description of Maxent read the papers on Maxent (Phillips et al. 2006) and (Phillips and Dudík 2008).
If you are not familiar with Maxent we recommend doing the Maxent tutorial first to familiarize yourself with the software as this tutorial covers only what is new about the spatialMaxent extension and not the general functionalities of Maxent.