The idea here is that if you see your friends are around the corner at a cafe, you can chat with them to see if they want to hang out. For instance, I live on the west side of San Francisco, and my friends don't often come to my neighborhood. Swarm can tell me when one of my Foursquare friends visits the park near my house, so I could possibly pop over for a quick visit.
It's worth mentioning that Facebook's mobile apps now have a similar feature, called "Nearby Friends," which works a lot like Swarm to help you see who's nearby. Comparing the two services, I'd rather use Swarm because it's a dedicated place for sharing my location and seeing my friends' locations as well. Also, while I have a diverse list of friends on Facebook from all over the world, I tend to only friend people who are local on Foursquare. That means with Swarm I can see who's around my city, whereas on Facebook's Nearby Friends, I see people spread out all over map, which isn't helpful to me.
Make a plan
The other way Swarm helps you get together with friends is with the planning feature. Instead of inviting other friends to do something, you can use the app to make a plan and share it others to see if they want to join. Friends can comment on the plan, or simply tap the "I'm interested" button to let you know they'd want to join.
Your plan can be anything you want, from a vague idea about going out for drinks to something more specific, like "I'm heading to Central Park at 12 pm for a picnic, anyone is free to join to kick around a soccer ball, or relax with a few snacks." You can tag Foursquare locations in your plan, so your friends know exactly where you're headed.
Mayorships, stickers, and other extras
With Swarm, Foursquare is changing up how mayorships work. If you're unfamiliar, a mayorship is an achievement you unlock when you've checked into a location more times than anyone else in a given time period -- you become the "mayor" of that location.
In the past, you would compete against the entire Foursquare community to become a mayor. Now, you only have to beat out your friends for that title, which may give you a more level playing field. However, if you've worked for years to become the mayor of your local bar, all that effort is now wasted.
Swarm also includes stickers, which you can use when you check in to express your mood. The app gives you six to start, and you can unlock more as you check into more places. Not everyone will love them, but I think they add more fun to the experience.
Lastly, the app will keep track of places you check into over and over and will show you other useful tidbits about your activity. For instance, if you check in with a friend for the first time in a month, or hit a four-week streak of checking into the gym, the app will let you know.
Swarm takes some of the most playful parts of Foursquare and puts them into a separate app, where you can check into places around you, keep tabs on your friend's whereabouts, and make plans with them.
If you're not already on Foursquare, you might wonder why it's worth downloading another app to make plans with friends, when you can do that on most social networks. It really comes down to your needs. While Facebook is still great for planned out future events, Swarm is perfect for spontaneous get-togethers. And if you do use Foursquare, I highly recommend you download it, if only because checking in using the app is easy as can be.