In plain words
Only then does one become fit to offer the ideal. This is not so easy. Even so, by the grace of God it becomes possible to achieve it to any extent at all. Step by step, living His life in this feeling, living it so, He came to realise Satya to some extent, came to recognise it, and in the feeling "I am not merely a messenger; I am closely related to God", He said, "I am the son of God." That is, He went on drawing very near to Divinity
In the world, Avatāras are of five kinds. The Nityāvatāra. That is, living in an ordinary humanness, recognising our duty in daily life, offering an ideal life, growing Prema and sharing it out among many: that is the Nityāvatāra. The second is called the Viśeṣāvatāra. That is, appearing only for the moment, completing that task, gladdening the people and removing that trouble: this is the Viśeṣāvatāra. The third is called the Aviśeṣāvatāra. That is, endowed with aṃśas, taking just what is called humanness as the support, keeping the bodily state as the goal, and leading a worldly life with a spiritual outlook. The fourth is the Aṃśāvatāra. That is, endowed with some divine powers and with divine vision, giving fitting courage and daring to ordinary men, to one's fellow men. The fifth is called the Pūrṇāvatāra. Endowed with all powers, joined with the whole of creation, striving with full Prema to make humanity one. This is the very foundation of the kingdom of Prema
So, step by step, Jesus took Himself to be the Aṃśāvatāra itself, and to some extent He came to His end within the Aṃśāvatāra. He said, "I and My Father are one," but He did not let go of "Father". They are one, true; but He went on living in the duality of "I" and "Father". When He was nailed to the cross, at the very last, right up until His breath left Him, the one and only word He spoke was "Father, Father have You forgotten Me, have You forgotten Me, have You forgotten Me", He said, and gave up His life. That is, even at the end He kept the feeling "Father" stamped within Him. So this is the difference between the Pūrṇāvatāra and this. Jesus went on spreading the principle of Prema and the feeling of compassion over the world. But unfortunately, after Jesus passed away, for 350 years no one uttered His name. About Him, people kept up arguments and counter-arguments of many kinds as well. This is merely the utter folly that belongs to the ignorant.