An ERP software can be termed as consumer software and this enterprise application software is typically not bought and sold instead it is licensed for use. It may be licensed to be used by a company, on a particular computer or by other criteria such as number of users. Buying it once doesn't mean you can duplicate it and share it with all your friends, or even sometimes use it on all your own computers. For enterprise application software how you pay for that license and the term of the license can vary.
Today, a software license can be perpetual. This means you pay for it once and can use the enterprise application forever. Even in this case more often a perpetual license agreement might have a stipulation that you have the right to use that software only for as long as you continue to pay maintenance to the software vendor that provides the product.
A maintenance agreement, which is a recurring cost, typically provides both technical support and certain innovations. Some of those innovations will be included in your maintenance fee and others may still need to be purchased. Maintenance is typically priced as a percentage of the software license.
But perpetual licenses are not the only type offered. Instead your license might be for a specific period of time. This is generally referred to as a "term" license. At the end of the term, you must either renew the license or discontinue use of the software.