Juxtaposition and contrast are both literary techniques involving the presentation of differences, however they cannot be used interchangeably.
Juxtaposition refers to the deliberate placement of two or more things side by side for comparison or contrast. This can include words, images, or characters, and the purpose is to draw attention to specific aspects of the work.
Contrast, on the other hand, is a broader term that refers to the noticeable differences between two things. It can be intentional or accidental and can be achieved through various means including, but not limited to, juxtaposition-like descriptions.
In short, juxtaposition is the intentional placement of things next to each other to highlight their relationship (similarity or difference), whereas contrast is a broader term referring to the observable differences between things, whether they are juxtaposed or not.