Deism is the belief that a supreme power created the universe and that this, and other truths, can be determined using reason and by observing the natural world.
For deists there is no need for faith, nor organized religion in order to come to these conclusions. Most deists don't see holy books and divine revelation as an authoritative source, but rather as interpretations by other humans.
In the words of Thomas Paine, an author, inventor and one of the Founding Fathers of the United States:
"The true Deist has but one Deity, and his religion consists in contemplating the power, wisdom, and benignity of the Deity in his works, and in endeavoring to imitate him in everything moral, scientifical, and mechanical."
There are various verbal evasions deists use when referring to 'God'. Some of those are Divine Watchmaker, Supreme Being, The Grand Architect of the Universe, Father of Lights and Nature's God.
Elihu Palmer (1764-1806), an advocate of Deism wrote:
"Deism declares, that the practice of a pure, natural, and uncorrupted virtue, is the essential duty, and constitutes the highest dignity of man; that the powers of man are competent to all the great purposes of human existence; that science, virtue, and happiness are the great objects which ought to awake the mental energies, and draw forth the moral affections of the human race."
Pandeism is a pantheistic form of deism, or a belief which is a mixture of pantheism and deism. Simply put, God as a supreme being created the universe and then became the universe. Some pandeists additionally have the belief that at some point all of the universe will coalesce back and again become God.
Some pandeists refer to God as the Deus in order to differentiate their ideas from those of theists.