Answer:
Sentences can be inverted (have their words arranged differently), or have certain words replaced with others, in order to convey a similar meaning as the original sentence, but better suit a situation.
When a sentence is inverted, its words are rearranged; certain words may be changed in order to help the sentence to make sense. For example:
'A flock of birds flew over the courtyard.'
'Over the courtyard a flock of birds flew.'
The words used in sentences can also be changed. This is done for a number of reasons; sometimes, so as to add flare or detail to a sentence. For example:
'The dog jumped over the fence and ran across the field.'
'The dog bounded over the fence and raced across the field.'