K-Means is one of the most commonly used clustering algorithms. It clusters data points into a predefined number of clusters. The K-Means-AS node in SPSS Modeler is implemented in Spark.
For details about K-Means algorithms, see https://spark.apache.org/docs/2.2.0/ml-clustering.html.1
Note that the K-Means-AS node performs one-hot encoding automatically for categorical variables.
1 "Clustering." Apache Spark. MLlib: Main Guide. Web. 3 Oct 2017.