What is the difference a aptitude and an interest?

Answer: Aptitudes tell you something about what sort of skill might be readily acquired, given sufficient training opportunities, but they are not sufficient to predict the precise sets of skills that individuals will ultimately develop. Likewise, interests provide a direction to the development of one's habits and activities

aptitude is something you can do well or have an ability to do well and interest is having a preference for a certain thing.

Explanation:

Aptitude is a combination of characteristics that indicate if you have the skills or are able to acquire the skills needed to do something. Interest is a having a interest in a skill or subject regardless of skill set.

Aptitude: Can you do it?

Interest: Do you want to do it?