Exersaucers are basically stationary swingers or jumpers that allow the baby's feet to touch the ground and allow babies to remain upright while playing with available toys and taking in the action around them (typical products of this category are the Fischer Price Jumperoo, the Evenflo Exersaucers, the Baby Einstein Discover and Play Activity Center and many more).

• Exersaucers have this benefit vis-a-vis walkers: They are not mobile. As they are stationary play centers, they do not allow babies to move around a room. This secures a very low rate of accidents. Paediatricians in fact encourage parents to opt for exersaucers instead of walkers, when it comes to keeping a baby busy in upright position (check scientific sites on the internet for further information).
• Exersaucers however have this disantvantage, compared with traditional playpens (or with floor activity supervised by the parent): They keep the baby in a restrained upright position, not allowing the baby to explore its own body and experiment with new moves. In this context, no exersaucer has been proved to actually promote mobility training of babies. As they are stationary they should be bought on the complete understanding that their role is basically restrained to keeping a baby busy in an interesting and safe way, but not as "exercising" your baby in training it to walk or stand as their name may suggest.