They are soft contact lenses with a very limited lifetime. That means that you have to replace them frequently and always use almost new and clean contact lenses. Of course they need to be cleaned too. Everything that applies to the normal soft contact laenses applies here as well.
The most common confection is the 6pack with 6 lenses of the same power. Wich means that if you need different powers for each of your eyes you will neel to buy two 6packs, one for each eye. But there are also some 3pack confections from other companies.
The life time of these lenses can vary from tree months, one month (the most popular), one week and one day (the newest addition). Their price can vary from company to company and many times it depents on their marketing strategies.

Advantages and disadvantages between disposable and normal soft contact lenses:
Advantages:

• Healthier. You have to change them so often that they do not have time to get too "dirty".
• Small cost of replacement. In cases that you lose your contact lenses often or they tend to get ruined often for example because of your proffessional activities (a hairdresser could easily ruin the contact lenses with a fixant spray) the cost of replacement of the disposable contactlenses will be much less than the normal ones.
• Occasional use. Disposable contact lenses are a good solution if you need to use your lenses occasionally and not on a daily basis.
• If your degree of myopia or hyperopia changes frequently (for example in individuals younger then 18 years old) and until now you did not use contact lenses for that reason , the disposable contact lenses are a good chance for you to try them.