Diary studies require you to complete tasks over a set period of time and record your thoughts/ findings.
To successfully complete a diary study, you need to complete the daily, weekly, or monthly required tasks within the time frame provided in your invitation. If you don't perform all the tasks as expected, you won't qualify for full payment.
Because you have to commit time to participate in a diary study, payments for these studies are often higher than $10 (USD). You can always check the actual payment amount in the study invitation email.