On Election Day, as votes are counted and news outlets wait for racial results and projections to report on, exit polls are an important tool that provides an early view of who is voting and what motivates their decisions.

An exit poll is a survey of voters leaving (or leaving) their polling location. It is the only national poll of known voters in the country. It allows news organizations, researchers and voters to understand what is happening in an election once the results are in.

Here's how election polls work, where they're conducted, and how NBC News will use election poll results on election night and in the days afterward.

Who conducts the exit survey?

Since 2003, Edison Research, a company specializing in election data collection, has conducted election polls on behalf of the National Election Pool. The NEP is a consortium of media networks – ABC, CBS, CNN and NBC News – that pools resources for a joint vote count and final polling process. NBC News independently analyzes and reports the exit poll results.

What questions are asked?

The exit poll asks voters which candidates they supported for president and other races. However, a number of other attitudinal and issue-related questions are also typically included, such as: “What is the most important issue for your vote?” The other key component of an exit poll is the question about a voter's demographic characteristics such as age, Gender, race and education. These types of questions help illustrate how different groups voted and what was important to them. They are also used to weight the exit poll – that is, to ensure that the exit poll accurately reflects the demographic makeup of the electorate and the election results.

Members of each news organization in the NEP collectively determine which states will conduct the exit polls (in addition to the national exit poll), and they work together to decide which questions will be included in the national and state questionnaires. The exit survey questionnaires consist of approximately 25 questions and take approximately 5 minutes to complete.

How are exit surveys conducted?

The poll is then conducted at a random sample of selected polling stations across the country and in states that have their own polls (more on this later). On election day, each polling station will be assigned at least one interviewer. This year, interviewers will be stationed at 600 polling locations across the country, each of them having to abide by local rules about where they can stand in relation to the polling place. The interview is self-conducted, meaning the respondent fills out the survey independently. Interviewers then announce their findings throughout the day, and the results are reported to news organizations.

What about state polls?

In addition to a statewide exit poll that tracks voters across the country, there are exit polls specifically for states that are critical to winning the presidency or include key voting rounds such as Senate or gubernatorial. This year, NBC News will cover state election polls in Arizona, Georgia, Florida, Michigan, Nevada, North Carolina, Ohio, Pennsylvania, Texas and Wisconsin. The polling will be conducted at 40 polling stations in each state.

How does the exit survey capture the growing proportion of people voting early or by mail?

The exit poll complements in-person interviews on Election Day by contacting early voters via a telephone survey of people on voter rolls in all 50 states and collecting interviews during early in-person voting periods.

This year, the exit poll is conducting interviews at early in-person voting sites in Georgia, North Carolina, Nevada and Ohio. All voters in a given state are asked the same questions, regardless of whether they vote early or on Election Day.

Are exit surveys anonymous?

Yes. Voters are personally handed a piece of paper and a pencil so that they can fill out a paper questionnaire, which they answer anonymously. When they are finished, they place their folded questionnaire in a box, similar to when they cast their vote. During telephone interviews, no personal information about the voter interviewed is stored.

How many people will be interviewed?

The statewide voter survey will include approximately 20,000 total interviews, including in-person interviews on Election Day, in-person interviews during early voting, and telephone surveys to engage other early voters, including those who cast their ballots by mail. For each state exit poll in Arizona, Georgia, Florida, Michigan, Nevada, North Carolina, Ohio, Pennsylvania, Texas and Wisconsin, there will be a sample size of 1,500 to 2,500 respondents per state.

How do we use exit surveys?

The NBC News Decision Desk uses some election poll data to predict election results. However, the election survey is primarily used for reporting on election night.

The data gives viewers and readers insight into the issues that motivate voters, how they think about the country, and who they are. It's the nation's first look at what the electorate looks like and how voters feel about the election, the candidates and their decisions.

What data do news organizations report and when?

NEP participants do not report exit poll results before 5:00 p.m. ET on Election Day, and no exit poll results that can indicate the outcome of an election are reported until all polls in a state have closed. As election night progresses and on-site interviewers collect more poll results, the data is updated and reweighted in real time.