Dropbox is an internet (aka cloud) based storage utility that you can use to store and share files. It's like having a 2GB thumb drive available wherever you can get internet access.This can be very useful if you need to send a large number of photos or documents to many people, or if you want to access files from multiple devices, e.g. from your home computer, from your smartphone, from a work computer. You just upload the files to dropbox and send out links to friends or the people that you want to share these with. This is much easier than trying to send multiple emails with photos attached. For every person that you get to join up to dropbox you also get 500MB of space added to you quota, up to a maximum of 16GB. There are also paid options for increasing the amount of storage you have available, but you get 2GB for free when you signup.

Dropbox is also smart enough to know what parts of a file have changed and will only upload the changes, so you save on time and bandwidth costs when synchronising files. Dropbox maintains a secure connection when accessing files and ensures that only the people you authorise will get  access to the files you share.

Another benefit of Dropbox is that it can be used as a backup for important documents stored on your computer. For example, if your hard drive fails, or computer gets stolen, you can still access the documents you have stored on Dropbox from another computer or device.

Dropbox is not the only cloud storage service available, but it is very popular and and has many 3rd party integrations. Some other options you may want to consider are Amazon's cloud drive, Microsoft's Skydrive and Google docs (soon to be called Google Drive) amongst others. One thing to consider though is that your data will be stored in other jurisdictions and will be subject to the laws of those countries (typically the USA). If privacy is a concern then read the privacy policy thoroughly to be certain that your information will be used appropriately. For more information check out the following links.