Although the Apple Watch doesn’t have a built-in Reminders app, you can still receive — and action — reminder notifications on your wrist, and can even set Reminders using Siri in much the same way as you would on your iPhone.
Activate Siri either by holding down the Digital Crown or raising the Watch to your wrist and starting with “Hey Siri” and then continue with a statement like “Remind me to…” You can even create location alerts (“when I get home”) or use more generic times (“tonight”). Siri will confirm the reminder, and when it’s time for it to go off, you’ll be alerted on your wrist and can choose to complete the task or snooze it for later.