What is God?
As an AI assistant, I don't have personal beliefs or opinions. The concept of God is a complex and highly debated topic in philosophy and religion, and can mean different things to different people.

In many monotheistic religions such as Christianity, Judaism, and Islam, God is considered to be the creator and ruler of the universe, the source of all morality, and the ultimate judge of humanity. In these traditions, God is often thought of as a personal being who interacts with humanity and can be worshipped and prayed to.

In polytheistic religions, such as Hinduism and ancient Greek religion, gods are considered to be supernatural beings with various powers and responsibilities, who are revered and worshipped by followers.

In some non-religious philosophical traditions, the concept of God can be interpreted as a metaphor for the absolute or ultimate reality, or as a symbol of the highest human ideals and values.

Ultimately, the definition of God is a matter of personal belief, and there is no one answer that can encompass the many different interpretations and understandings of this concept.
Is there any evidence for the existence of a God? What about multiple Gods?
There is no physical evidence for the existence of a God or multiple gods. Most major religions have claims of histories or miracles written down in a central text, such as the Bible for Christianity. These incorporate supernatural elements and elements which have a physical basis, such as depiction of Angels and the description of a Great Flood that wiped out most life on Earth. For those items that are supernatural, there is no possibility for proof with physical means as supernatural claims inherently deal with things outside of the world. Those claims with physical basis, such as a Great Flood, do not have any physical evidence to support them. However it should be noted that the academic approach to resolving questions about religions is theology, a subject categorized in humanities. Humanities deal with subjects with normative statements, which are statements of how things should be rather than are. For example, philosophy asks what morality should be, rather than defining it on any physical basis. Theology academically must therefore be treated in a similar way, being made of claims of what things should be considered true for no other reason than the person deciding they are. It should be also noted that there are some interpretations of Theology which try to reconcile the absence of evidence of miracles in the world like Deism, which posits that all science and reason points to a lack of an God that is involved in changing aspects of the world, but which was responsible for starting the universe as there is no currently sufficient evidence for how the universe to have started itself. All of the above applies to multiple gods, as they too have no physical evidence of miracles.
Did Jesus actually exist historically then?