Bouncer (or bouncy) seats generally consist of a frame made of thick metal wire, tubular metal, heavy-gauge plastic, or wood. Covered with a soft (and preferably removable and/or washable) pad that conforms to a baby's shape, bouncer seats are usually springy and bounce or rock when a baby moves to keep him relaxed and amused. The fabric seat is rounded to support a baby's still-fragile spine, and the semi-upright tilt gives him a view of the surroundings. A bouncer may also be more comfortable for some babies than lying in a flat crib after they've eaten.
As you read about types and features, you'll discover lots of variations on the basic bouncer seat, including models that rock as well as bounce, battery-operated versions, models with toys attached, and bouncers that play music. Given that you should only use a bouncer until your baby is 6 months old and that you shouldn't leave her in it for long periods of time, we think a basic, baby-powered model is just fine for most babies.
That said, if you do choose a battery-operated model, one feature you might find useful is vibration. If your baby needs a little help falling asleep, a seat that vibrates can be invaluable because it imitates a lulling car ride. In any case, if your baby falls asleep in her bouncer, don't leave her alone. Keep in mind that the safest place for a baby to sleep is on her back in a crib on a firm mattress.
Once your child reaches the weight or age limit for a bouncer or can sit up--whichever comes first--you should stop using it unless it's also intended for older babies and toddlers. There's a risk of tipping when a child who's too big or too active uses a bouncer.
Most models have a detachable play bar (sometimes covered with padding) or an overhead mobile of plastic or fabric-covered toys for your baby to kick, bat, or gaze at. Some models have colorful lights and sound effects that respond to a baby's movements and/or vibrate at different speeds to lull him to sleep or entertain him. Some models simulate nature sounds or heartbeats, play music, or let you plug in your own portable music device. Others transform your child's smallest movements or your own footwork into a soothing rocking motion without batteries. Some versions can be folded for travel.
You can expect to use a bouncer until your baby can sit up unassisted (around 6 months or so) or reaches the recommended weight or age limit, whichever comes first. The typical weight maximum is 25 pounds, with an age limit of 6 months. But some models are suitable for babies who weigh 28, 30, or 40 pounds, so they can be used as toddler chairs, too, when the seat back is raised to a comfortable upright position and the toy bar or restraint system is removed.