Research methods
Loaded question
A question that contains an assumption the respondent may not agree with, so any direct answer accepts it. 'Why do you prefer our app?' is loaded.
A loaded question builds in a premise. Asking 'What do you like most about our checkout?' assumes they like something about it. Respondents who disagree either play along or skip the question, and both distort the data.
Split the assumption out: first ask whether they have used the checkout, then how it went.