On-line

On-line software will use network resources such as shared files or the internet. Email is an on-line piece of software, however you can use it offline too.

Off -line

Software that does not require a network connection in order to function.

On-line/off-line duality

Software rarely falls neatly into one of these categories. For example email can be used offline to read emails offline. Also word processors can be used online in order to download extra clip art or save a file onto a shared drive. Software, especially modern software, tends to have both on-line and off-line elements. Even computer games follow this pattern. Most modern PC games have some form of multi-player mode that can be run over the Internet.