A query engine is required in order to execute SPARQL queries over a dataset. Query engines may be embedded in applications, or accessed remotely. Remote access may be through a vendor-specific API, or through the SPARQL protocol if an implementation supports it. This documentation will not cover how to submit queries through specific vendor APIs.
SPARQL Endpoint implementations typically provide a user-friendly web interface for submitting queries and viewing their results. Public SPARQL endpoints (such as DBPedia) can serve as useful datasets for non-mutating examples.
If you wish to configure a private SPARQL Endpoint for experimentation, Apache Fuseki provides a free and platform independent option.