To answer this question more appropriately let us first answer ” who is an asignee ?”
Any person or company to whom you sell the complete rights of your Patent is the assignee of that Patent. In case you are not selling it to anyone you remain the assignee of the patent. However, in case, you are working for a company and in the course of your work you have invented something, the company you work for will be the owner of the invention [it depends on the agreements you may have signed with them].
A person to whom you assign the complete rights of you patent is the assignee. A good analogy can be something like selling off your property. Whereas, licensing is like providing temporary [or limited] rights to someone, the analogy could be putting your property up for rent for a certain period of time under certain stipulations and terms. The main difference is ownership. The owner of a patent possesses the right to exclude or include others from using the invention. Let’s take an example, initially an inventor owns a right over the invention. During assignment the inventor can give his rights to someone else, for example a company he works for. The assignee then becomes the owner of the patent and has the right to exclude or include other from using it. Thereafter, the assignee may choose to have a license agreement that permits another company to use the invention under certain conditions. However, the assignee here does not necessarily give up his right, they still remain the assignee and are merely giving permission or a license to another company [the licensee] to use their invention under certain conditions.