Yes, a poll is a single question or prompt you are inviting your audience to interact with.
A multiple choice poll lets you define a set of fixed choices that participants can choose from. Results can be displayed in a graph. An example of a multiple choice poll might be, "Which candidate will be President in 2009?" with options like "McCain", "Obama", and "Other".
A free text poll allows participants to send free-form text responses instead of fixed choices. A free text poll might ask, "What questions do you have for the presenter?" and participants can send in any short answer they want. Their answers might be just one word, a short phrase, or an entire sentence.
A goal poll adds up numeric contributions in a rising thermometer. Goal polls are commonly used for encouraging participation at fundraisers. People in the audience can text in a pledge to donate a specific amount, followed by an encouraging comment.
You can display your audience's answers in real time on a projector for everyone to see, or just on a laptop in front of the presenter. Some polls are not used in live-event settings (for example, radio, print, or long-term exhibition voting), so a live display of results isn't that relevant.