Children
In Generations, they'll have access to many more activities by way of unique new items that have been requested by the Sims 3 fan community, such as a costume chest and the long-awaited tree fort. The costume chest lets children change into a variety of different costumes, which then let children play-act different fantasy scenarios. For instance, one costume is of a giant, Godzilla-like monster, and lets children go on a mock rampage, smashing their blocks like imaginary city buildings. Children can climb into their tree forts to give blustery speeches to their imaginary royal subjects, or to toss very real water balloons at their very real older siblings.

However, the most interesting new feature in this new expansion seems to be the imaginary friend, a character that your child creates after ordering a specific type of mail-order doll. After giving the doll a name, your child sim can summon an imaginary, child-sized version of the doll to be a playmate who will happily hop onto the opposite end of a seesaw and even run minor errands for you if you have a decent enough social relationship with it. Playing with your imaginary friend fills up your child sims' social motive in the same way that socializing with real people would. Even more interestingly (and more than a little weirdly), as children grow into teenagers, they can not only keep their imaginary friends around, but they can also develop a romantic interest in their make-believe buddy.

Teen

Those teens who aren't romancing their favorite childhood doll can busy themselves with Generations' new prank system, which lets young hooligans express their disregard for authority by way of such dastardly gags as the old doorbell dash (ringing a neighbor's doorbell and running away before they can answer), covering a neighbor's house in toilet paper (or "TP'ing"), and leaving a flaming bag of something or other on the doorstep of a neighbor you just know owns a brand-new pair of penny loafers. Pranks can contribute to your teen's social standing and will actually let you build up a reputation as a master prankster and local legend to the other kids at school, but if you get caught, your teens can be grounded, which means revoked privileges and negative "moodlets" (The Sims 3's system of minor mood-changing conditions that can either boost or detract from your characters' overall well-being).

Other ages

new events for adults intended to let players create even more-memorable events to be photographed and shared via the expansion's built-in social media functionality, which will let you upload your favorite cherished moments directly to Facebook. These adult events include a rated-T-for-teen bachelor party, during which you can hire a female "dancer" to pop out of a wedding cake and spray the lucky bachelor with a bottle of "nectar" (the adult beverage of choice in The Sims, bottled from grapes in the finest vineyards of France in The Sims 3: Ambitions). At an event like this, it's also entirely possible for the best man (or the jealous fiancée) to sneak in a few incriminating photos and nail the groom with them later--just one example of the kind of new memorable moments that Generations will provide.

Source: IGN.com