The following sentence is a run-on: The Merchant of Venice is an interesting play it is about a young man named Bassanio, who falls in love with wealthy girl, Portia.
It should be re-written the following way:
The Merchant of Venice is an interesting play. It is about a young man named Bassanio, who falls in love with wealthy girl, Portia.
The sentence is two sentences fused together as one, which makes it a run-on and also difficult to read. When the proper punctuation is used the sentence is no longer a run-on and is then easier to comprehend.
