Answer:
A fused sentence is when you squeeze together two sentences with no punctuation in between. A fragment is when you have an incomplete thought/sentence that does not generally make sense when used on its own.
These should not be used in writing as the sentences do not even make sense when read. Both of these do not clearly convey the message that the author is trying to send.
Step-by-step explanation:
Fused Sentence Ex. The lion roared the children screamed.
Fragment Ex. Because of the rain.