For cardio, there are two categories: slower, steady-state cardio and high-intensity interval training, or basically sprints. The former is nice and plodding, the other is hard and heavily favoured by fitness enthusiasts. Both have their merits, but here's how to know when one makes more sense than the other.
A 45-minute run at a nice pace is a good example of steady-state cardio. You get great exercise benefits and probably feel great after. The main issue is, it is still 45 minutes of your time. High-intensity interval training (HIIT), by contrast, is short and bittersweet: you get similar cardio benefits in less than half the time, but it's so uncomfortably intense you might feel sick after.
And because it's so intense you continue burning kilojoules (not much) long after you're done. If you care about your physique and time spent, HIIT would suit you.
HIIT has its downsides though: it's so demanding on your body that you should only do it a few times each week and it's easy to get injured. Some people don't have the heart or joint health to handle HIIT at all. Meanwhile, steady-state cardio is a safer option for most people, can be done more often and is a way to actively recover from heavy weight workouts. Both have a place in your routine, so do the one you can fit into your routine and enjoy doing (but don't overdo it).