What is curve file in corel drawn why we do curve file
"curve" is any vector object,
Some objects has special features, such as rectangle, circle, text, etc
if you "convert to curves" those objetcs, that means they lose those special options.
for example, if you select a rectangle with the shape tool, you can round corners manually. But if you convert to curves this is no longer possible, if you select a node you will mode it but the option of rounded cornes was disabled.
On the same way, if you select any text and convert it to curves, it becomes a drawing, you can't change the font or add/modify the text.
Some companies ask for files "converted to curves" in order to avoid the check the text, and also prevent a missing font.