You can't always stay home, and portable potties are a necessity when potty training your toddler. Life doesn't stop and neither do vacation plans, day trips, or visits with family and friends. In the early stages of potty training, your toddler may not be able to notify you early enough to run across the park to the public bathrooms. Sometimes they don't know until it's too late and sometimes those public bathrooms aren't fit for naked bottoms.
Portable potties are perfect for those trips away from home and within the home. They are light to carry, compact, easy to setup, and can be whipped out as soon as you hear that frantic cry "Mommy, I gotta go!". They can be your first line of defense to catch accidents before they happen. In the home, portable potties can be moved from room to room so your toddler always has a place to go wherever they may be playing. If your toddler needs a visual cue to remind them to use the potty when they get the urge, a portable potty will be that reminder.
When traveling, porta-potties can be indispensable. They go where you go: the park, the car, the beach. You don't have to interrupt your potty training to go on vacation or away for day trips or revert back to diapers for a day. After being introduced to training underwear, most toddlers don't like to revert back to diapers. Soft training pants do feel nicer, but when your toddler isn't at the stage where they can hold it for more than 30 seconds, a portable potty can save you from telling your toddler to hit the lake.
Portable potties are usually full chairs, either hard plastic or inflatable. Some are simple adaptable potty seats that fold in half with an attached carrying handle. Many chair style portable potties use plastic bags with disposable, absorbent liners to catch your child's offerings. You tie the bag shut, then empty the contents in a toilet when near one, and throw the used bag and liner in the garbage. Some portable potties are equipped with the plastic catch bowl that you need to empty, similar to normal potty chairs. High-end portable potties offer a leak-proof system that seals everything inside the chair until you can empty it.
It may take some time for your toddler to adjust to using a potty in public. You may not always have compliance. Try to find a quiet, secluded spot to set the portable potty up, especially in the beginning, until your toddler is used to peeing with an audience.