What is a referendum? What is an initiative? What is a recall?
A referendum is a general vote on a particular issue that is singular in the political arena of the area of the electorate. This is different from voting for a candidate, and is typically brought about by public outcry and debate on a particular subject. An example is perhaps gay marriage referendums.
A recall is an election that gives an electorate a chance to vote out a previously elected official if they feel that the person is not doing a good job, or is not acting in accordance to the position he or she holds. The recall elections occurs while that person is still in office and filling out his or her term, and there is a direct vote upon whether or not the person will retain the position or be removed.
An initiative, or a ballot initiative, is often a grassroots effort to place a particular issue onto the ballot so that an electorate can actually vote to pass it and not wait for legislative action from elected politicians. This is an example of the way that direct democracy functions in the American system, but typically only up to a state level.