Merger & Acquisition difference, between, please, terms

Windjammer

Can some body please highlight the difference between Merger & Acquisition? Are these terms used interchangebly or there is any strict distinction between these two?

giorgio10

The curriculum says
“In a subsidiary merger, the company being purchased becomes a subsidiary of the purchaser, which is often done in cases where the company being purchased has a strong brand or good image among consumers that the acquiring company wants to retain”
This is making me confused as the other company is still existing though as subsidiary. Moreover is willingness of the management has to do anything with classifying as merger or acquisition?
Curriculum also says
“An acquisition might refer to the purchase of assets from another company, the purchase of a definable segment of another entity, such as subsidiary, or the purchase of an entire company, in which case the acquisition would be known as a merger.”
I think Merger is a special kind of acquisition where the whole company is purchased and the entity may or may not exist.