NEuler is a graph data science playground application designed to help users execute and understand graph algorithms in Neo4j, allowing them to quickly import example data, execute various graph algorithms, and visualize their results with tools like t-SNE scatter plots. Users can set up the Neo4j sandbox environment by following a link or selecting an existing one, then choose to run a single algorithm, such as node embedding algorithms like Node2vec or FastRP, which calculate fixed-length vector representations for each node in the graph while preserving properties like graph structure and information. By configuring parameters and running the algorithm, users can observe the results in table form, click on the Scatter Plot option to visualize the results, and export code needed to execute the algorithms outside the NEuler application. The Neo4j Sandbox projects offer a range of datasets for users to experiment with, including Twitter, Open Street Map, and contact tracing projects.