Mindfulness can be practiced any and every moment of the day. To practice mindfulness, it's as simple and as hard as focusing on the present moment. So when you're washing the dishes you're focused on washing the dishes and not what you're going to make for dinner or talking to your partner about a movie you've recently seen, etc. It's common to practice mindfulness for a short period of time because it's actually difficult to focus on the present moment all day every day. And sometimes it might not be beneficial or appropriate to practice mindfulness.
Meditation is an activity. My experience is in silent meditation, meaning someone sits in silence. But there are different meditation practices including when someone repeats a phrase or mantra to themselves, guided meditations where the person sits and listens to someone speaking or a recording, and walking meditations where the person is moving rather than sitting. Meditation times can vary from a few minutes to hours. Meditation can be a practice on its own or can be a part of a mindfulness practice.
A common misconception of meditation is that a person is supposed to stop thinking thoughts to meditate. That's not possible. Silent meditation instead should focus on letting the thoughts go by without trying to focus or examine them. Or, if there's a guided meditation or a mantra repeated, if the person finds their mind wandering, to just gently bring it back to the meditation words/mantra without judgement.