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.

See K-Means Algorithms for more details.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.