Definite award is one where a specific quantity of goods is delivered by a specific date. It can also be a service of a short duration where the quantity and price are known.

Examples:

Delivery of 1000 widgets by March 31st.

Job of installing an upgrade for an office over the period of a week.

Indefinite award is one for a contract that starts on a certain date and goes on for a period of time such as a service or requirements contract. The exact quantity or cost of the total service may not be definite.

Examples:

Tree trimming services from January 1st to December 31st. 

Contract for a supplier of widgets From July 1st to  June 30th where widget orders will be placed periodically or as needed.