As was previously mentioned, there are different types of lots in the game - housing, business, industrial - and finally the sort that the Park is part of - Community Lots.
The Park is the first part of an expanding collection of Community Lot structures - there is a Skate Park as well and that should give you an idea of the point to these - but even though these are town-owned and funded, they do generate XP which is nice.
Each Community Lot building or destination has a series of goals attached to it as well... How you complete many of those goals requires you to have your Sims visit the Park.
Considering all of the things you can do there, the Park should be an early build.
Visiting the Park is accomplished by going to the town menu and then selecting the Park, at which point you enter the Park and can then use the Sim Tracker to call your Sims to visit the Park. Once they are there, they can participate in the various Park-based activities.
- Barbeque: Placed strategically in the Park are some Bar-B-Q's that you can use -- Use BBQ (30m / 60 XP), Grill 'Em All (8h / 430 XP), or Double Smoked Pulled Pork (20h / 810 XP).
- Chess Board: Located in the corner of the Park are some Chess Boards with outdoor pieces that you can play with! Play Chess (10m / 30 XP).
- Lake Fishing: Basically clicking anywhere that there are no ducks offers you the chance to use the Lake itself, allowing your Sim to Go Fishing (4m / 10 XP), Unwind (1h / 100 XP), Settle In (9h / 300 XP), or have a 12 Hour Fishathon (1 Day / 600 XP).
- Lake Ducks: Simply clicking on the lake where the ducks are swimming presents the option to Feed the Ducks (15m / 40 XP). This activity also qualifies as a Social Action, and will raise the Social Stat.
- Lake RC Boats: Tapping on the Lake where the RC Boat course is located gives your Sim the option to Play with RC Boat (30m / 153 XP).
- Park Bench: Sitting on a park bench and daydreaming is just the thing if you cannot decide on something else to do, and you have the option to Daydream (1m 30s / 10 XP), Rest Eyes (3m 20s / 25 XP), Have a Nap (1h 30m / 125 XP), or to Catch Some Z's (3h 30m / 265 XP).
- Park Toilet: If your Sim is in need, no need to rush home! Use the Park Toilet (30s / 6 XP).
- Soap Box: In the Park there is a soap box (seriously) that you can stand on to make a speech -- which will naturally increase your Sims skill in that skill. The options are Make a Speech (15m / 40 XP), Occupy Park (4h / 300 XP), End is Nigh (12h / 820 XP), and Warn Simanity (1 Day / 1200 XP).
- Tai Chi in the Park: Practice Tai Chi (1 Hour / 100 XP) - or - Reach Nirvana (12 Hours / 570 XP) The ancient art of Tai Chi, practiced on a mat in the Park, among the flowers and trees and peaceful... Ah, well, it will earn you XP in the doing of it!
Even when you are not fulfilling goals the Park is a great place to visit if you want to work on social actions or pick up some extra XP in a sunny and happy environment....