The corrected sentence without unnecessary words and with proper grammar: "The girl with curly hair runs every morning on her way to school and is never late." Here's the breakdown: - "What is this group of words?" has been removed because it does not contribute to the content of the sentence. - "and she runs" has been shortened to "runs" to eliminate redundancy. - "but don't you worry" has been removed because it is an informal phrase that does not fit the context of the sentence. - "because she is never late" has been changed to "and is never late" to connect the clauses smoothly, making the sentence more concise. This revised sentence eliminates the issues of a comma splice, run-on sentence, and fragment.

Answer: The group of words you've provided: "The girl has curly hair and she runs every morning on her way to school but don't you worry because she is never late." is a run-on sentence. A run-on sentence occurs when two or more independent clauses (each of which could stand alone as a separate sentence) are connected improperly without appropriate punctuation or coordinating conjunctions.

Extra: Run-on sentences can often be confusing for readers because they can make the text feel rushed and make it harder to understand the separate points being made. Here are some terms related to sentence construction that will help to understand the concept better:

1. Good Sentence: A properly constructed sentence that has a subject, verb, and expresses a complete thought. An example would be, "The girl has curly hair."

2. Comma Splice: This is a type of run-on sentence where two independent clauses are joined with a comma but without a coordinating conjunction. For example, "She runs every morning, she is never late." The correct version would be to add a conjunction: "She runs every morning, and she is never late."

3. Run-on Sentence: As mentioned above, this is when two independent clauses are joined without proper punctuation or conjunction. To fix a run-on, you can separate the clauses with a period, semicolon, or add a coordinating conjunction (for, and, nor, but, or, yet, so).

4. Fragment: A sentence fragment is a group of words that is punctuated as a sentence but does not express a complete thought, lacks a subject or a verb, or both. For example, "Because she is never late."

To correct the run-on sentence you've provided, you could break it down into separate sentences or use conjunctions and proper punctuation. For example: "The girl has curly hair, and she runs every morning on her way to school. But don't you worry because she is never late."