"Don't Ask, Don't Tell" (more formally, Directive 1304.26) is a nearly 20 year old compromise to allow the service of quietly gay and lesbian Americans in the military. It restricts the military's actions on identifying gay or bisexual service members and bars these same members from disclosing that they are gay.
Like most compromises, the policy has mollified some, displeased others. Unlike some compromise policies, however, DADT is about to be replaced by a better one. Keeping a promise made during his campaign, President Obama has been pushing Congress to repeal the law that banned gay soldiers from serving openly. I believe that they will do so this year.
I agree with the President and with most Americans on this issue. Openly gay people should be allowed to serve in the military. In fact, it is ridiculous to have to write that sentence.