Turtle is a syntax for expressing RDF data. Its syntax is similar to SPARQL. It’s a W3C standard. Its MIME type is text/turtle, and the file extension for turtle files is .ttl. It’s short for ”Terse RDF Triple Language”. It can be converted into JSON-LD. It’s a subset of a notation called “Notation3”, and thus valid Turtle files are also valid Turtle.
OWL can be expressed using Turtle. You can use Protege to open one and then save as the other.