A user segment represents a segment of your target audience. They are created by defining rules that include or exclude people according to their profile attributes. User segments are used within scenarios and targeters.
A renderer is a JSP fragment that provides the visual presentation of the content.
A slot is essentially a container that you can use to display and manage dynamic items on your Web site. It acts as a dynamic placeholder in the page that either waits for content (a passive slot) or calls out for it (an active slot). The content it retrieves is dictated by a scenario or targeter that has been created for use with that slot. The content is identified by either pointing to a specific repository item or a repository folder that contains multiple pieces of content.
A scenario is a choreographed series of interactions with your Website visitors and can be triggered by a specific event or profile attribute and controls when and to whom to deliver content.
A targeter is a set of business rules that can be used within a scenario to help define who should see the different content in your offer management panels. Targeters often use user segments to help define who sees what content.