Run-on sentences
Examples:

Although he never calls them by name, John Steinbeck immortalizes a 1930s labor group, the Wobblies, in The Grapes of Wrath, a novel about the life of the Joad family.

Run-on sentence

OK

This sentence is not a run-on even though it is long. It consists of a subordinate clause beginning with Although and an independent clause beginning with the subject and verb John Steinbeck immortalizes.

The Joads have lost their farm during the Depression, the family has come to California seeking work.

Run-on sentence

OK

This sentence is a run-on known as a comma splice; it consists of two independent clauses joined with a comma. To fix it, the writer could make the first clause subordinate by adding the word Because at the beginning.