Traditionally software vendors have licensed their software with a Perpetual Licensing model where the customers pay for the software usage license in advance.

The original license fee usually covers the cost of some software enhancements for a limited time. Some vendors offer an annual maintenance or simply version upgrades (at a fee) when new versions are launched.

The Subscription Licensing model is actually becoming more frequently used for software licensing.

It is generally a monthly usage fee (or a fee for a specific period of time).

Subscription licensing includes software updates and also new versions as they become available.

Shortly, in a Perpetual License you pay an endless license and you keep the right to use it "forever", “as it is”.

Shortly, in a Subscription License you pay a monthly (or yearly) subscription and you have the right to use it for that period of time, and if you don't renew the license is no longer valid.

This is the most common way of purchasing software products: the buyer gets a perpetual license to use the software (unlimited in time, under the terms of the user license).

Through the Subscription you are not buying software but the right to use it for a limited time (usually 1 month). It is as simple as downloading the software from Internet (shipping is not required) and installing it.

The software product includes the installation CD, the dongle (software protection device), the installation guide and a perpetual license to use. This product does not require permanent Internet connection.

At the end of the subscription period, the user can decide whether to renew it or not. Subscription requires that the computer has a permanent Internet connection while using the software.