Final answer:
The -primary class is used to set the color, while bg-primary is used to set the background color in Bootstrap.
Step-by-step explanation:
The difference between -primary and bg-primary in Bootstrap is that -primary is used to set the color of an element, while bg-primary is used to set the background color.
For example, if you want to set the color of a text to the primary color defined in your Bootstrap theme, you would use the -primary class. On the other hand, if you want to set the background color of an element to the primary color, you would use the bg-primary class.
Both classes are valid Bootstrap classes and are used for different purposes.