The answer is not: “a man-God who walked around on Earth for about 33 years, 2,000 years ago.”
‘Jesus’ comes from a word meaning ‘God is help’, and in Christianity, Jesus is often thought of as a ‘mediator’ between the divine and human, by partaking of both natures in some sense. It is only in a brief, limited way, however, that God, according to Christianity, in this sense incarnated in human form on Earth. I.e., ‘Jesus’ is often primarily thought of anthropomorphically – as being co-terminous with the human-divine being who walked about on Earth, but this is not right.
This can be better seen by considering the tradition within Christianity of equating Jesus with the Logos. The Logos is perhaps a better fit for the notion of the ‘living Christ’, i.e., an active principle in the day-to-day activities here and now, as opposed to an historical figure. ‘Logos’ is a word meaning something like ‘thought, word, ordering, wisdom’ (and its technical meaning differs from, say, Stoicism to neo-Platonism to various strands of Christianity).
One can use a simple metaphor to help understand the Christian trinity if thinking of Jesus as the Logos: God the Father is ‘mind’, God the Son is ‘thought’, and the Holy Spirit is the ‘breath’ which occurs when thought, which comes from mind, manifests as speech. They are three distinct aspects of one process. (Compare this metaphor with the image here, say.) In Christianity, the ‘divine wisdom’ or ‘ordering’ of things is constantly manifesting in the world. This is often what are called ‘miracles‘, i.e., ‘signs’, understood in the proper sense (non-chance co-incidings of things, attributable to God).
Using this analogy, the manifesting is ‘speech’, which comes from the divine ‘mind’, through the ‘thought’. I think this puts the historical notion of ‘Jesus of Nazareth’ into a better scope – according to Christianity, the historical episode is a particular manifestation of the divine wisdom.