Agnosticism is a belief that knowledge of the existence or non-existence of God is impossible. It is often put forth as a middle ground between theism and atheism. Understood this way, agnosticism is skepticism regarding all things theological. The agnostic may generally hold that human knowledge is limited to the natural world -- that the mind is incapable of knowledge of the supernatural.
From a Christian perspective, some would see agnosticism as a denial, like atheism, since natural revelation reveals to all, Christian or not, that there is a God, and special revelation, i.e. God's Word in the Bible, reveals the particular Christian, Triune God.
Atheism is the belief that there is no God, from the negative a + theism. While atheism may broadly deny the existence of any god(s) or divine beings, it most often is a denial of the God revealed in the Bible. This may be contrasted with agnosticism, which neither affirms belief in God (theism) nor denies God (atheism) but leaves the question of the existence of God open or declares it unknowable. From a Christian perspective, some would also see agnosticism as a denial, like atheism, since natural revelation reveals to all, Christian or not, that there is a God, and special revelation, i.e. God's Word in the Bible, reveals the particular Christian, Triune God.
Deism is a religion which accepts the existence of a Creator God, but rejects revelation (such as the Scriptures) and bases itself instead on nature and reason.
Henotheism is the belief that many gods exists, yet the worship of only one of these gods. A henotheist would admit that many gods have real existence and are able to be worshipped. However the henotheist chooses to worship only one of these gods. This sets the henotheist apart from the polytheist who worships many gods."  This phrase has historically referred to the context of tribal gods.
Monotheism is the belief that there is but one God. The term comes from the Greek monos "only", and theos "god". Monotheism opposes polytheism, the belief in more than one God, and atheism, the belief that there is no God. Other worldviews such as deism (the belief that God created but does not intervene in the world), and pantheism (the belief that God is in all and that all is God), do maintain that there is one God. However, the monotheism of Christ, formed by the words of the Lord Jesus and His Father in Heaven as quoted within the Holy Scripture, rejects these other worldviews, maintaining that there is one God who does providentially work within the world, while remaining distinct from it. The Christian doctrine of monotheism differs from those of Islam and modern Judaism by maintaining a belief in Trinitarian monotheism.
Panentheism is the view that the world is in God and yet God also transcends it (i.e. is somehow different from the world). Not to be confused with pantheism, which means God is the world, panentheism views the world in God and qualifies this by saying that he is still transcendent, or above the world. Panentheism holds that God is the “supreme effect” of the universe. God is everything in the universe, but God also is greater the universe. Events and changes in the universe effect and change God. As the universe grows and learns, God also increases in knowledge and being.
Pantheism comes from two Greek words, pan (all) and theism (God) meaning "all is God" or "God is all." It is the belief that all things contain divinity and that God is the sum of all things. Pantheism is the view that God is everything and everyone - and consequently that everyone and everything is God.
Polytheism is belief in, or worship of, multiple gods or divinities. The word comes from the Greek words poly+theoi, literally "many gods." Most ancient religions were polytheistic, holding to pantheons of traditional deities, often accumulated over centuries of cultural interchange and experience. Present-day polytheistic religions include Hinduism, Shinto, some forms of Wicca, Vodun, and Asatru. Buddhism is regarded by some non-practitioners as polytheistic although this view of the religion is rejected by most adherents. Some Jewish and Islamic scholars regard the Christian doctrine of the Trinity as bordering on polytheism, a view that Christians strongly reject.
However, there are some serious philosophical problems when thinking about the definition of God in relation to polytheistic beliefs. By the broadest definition in most dictionaries, God refers to the supreme being that is above everything else. By very definition, this requires that it be only One being. The reasoning is that if this being was just another one of many gods, He would not necessarily be the highest or supreme. A polytheist might reply that there is one highest God with multiple lesser gods (i.e. Henotheism). However, this is still in contrast to the definition because those lesser beings cannot be referred to as "God", simply because they are not the supreme being. The definition of a supreme God demands that He is One.
Relativism is the philosophical position that all points of view are equally valid and that all truth is relative to the individual."  In other words, truth is what you want it to be. "Relative" can essentially mean "wide ranging" or "not absolute". Thus, the relative mindset believes that any idea of absolute truth (something that is true irregardless of if someone thinks it is or not) is impossible.
Theism is the belief that God exists. God may be defined briefly as "...a single and simple spiritual being... eternal, incomprehensible, invisible, unchangeable, infinite, almighty; completely wise, just and good, and the overflowing source of all good."