Depending on where you are, depending on where you live, and the kind of trails that are offered in your area, the nice thing about trails compared to running on a track is the variety that it offers. You can find a hilly course, you can find a shaded course, whereas the track you'll be a lot more exposed to the elements, you'll be a lot more exposed to the sun.
Trails will give you a little bit more of a challenge. Again, if you find a hilly course you can work on a sport specific strength, and what I mean by that is when you're actually doing the sport that you're focusing on and building strength while you're doing that. Trail running can also be a little bit gentler on your joints and your body. The reason for that is because you have to be a little careful about your steps, so you end up taking shorter steps for the trail than you might be on the road or you might be on the track.
A great way to find trails in your area is going to Map My Run. It's a website. You can see where other people in your area have run. You can see routes that they have run. And just be careful about when you go out. If you are not familiar with the trails, look for a map or do a short route where you can just actually do an out and back versus maybe one big loop.
Get to know the trails in you area. What kind of terrain do they have? Do they have a lot of boulders? Do they have a lot of rocks? Are they by the river? But also if they are by the water it's a good way to keep you on track to where you're going. You can actually keep that as a landmark to make sure you don't get lost.
One other thing to consider when you're doing trail running is do you need another pair of shoes? There are trail running sneakers, other than the regular sneaker that you might wear for the track or the road. The nice thing about trail shoes is that they offer a little bit more stability in the meat of the shoe, in the sole of the shoe, and the tongue of the shoe is actually attached to the body of the shoe so that it prevents rock, small pebble, dirt to get in there.
If you're on a trail that offers a little bit of elevation change you may want to consider bringing an extra layer. If you're going to be climbing a little bit throughout the day, maybe you want to bring an extra long sleeve shirt or a light jacket in case it does get cold. Ultimately, trail running is a great way to vary up your running routine, get outside and have fun and be with nature.