( The 'y' in this name is pronounced like 'y' in 'you', the 'D' like a hardened sound of 'th' in 'brother', 'sh' like 'sh' in 'she' and 'th' like the hardened sound of 't' in 'tip'.)
Yudhishthira was the eldest son of Paandu and thus the first of the Paandavas. He was the son gifted by lord Yama to Kunthi. Ananthavijayam was the name of his conch.
Droupadi was his queen who was a common queen of all the Paandavas. Droupadi bore him a son named Prathivindhya. This son was killed by Ashvaththaama in the night of the eighteenth day of the war. Besides Droupadi, he had another wife Devika from whom he had a son named Youdheya.
Yudhishthira is also referred to as Paandavaagraja (=eldest of Paandu's sons), Kountheyaagraja ( = eldest of Kunthi's sons), Dharmaraaja ( = God Yama ), Dharmaja ( son of God Dharma ie Yama) and Ajaathashatru (= a man to whom no enemy was born) too.
He was manifestation of the god Yama himself.
Yudhishthira was known for his righteousness.
Though he is not free from vice, his conduct was exemplary most of his life. His respect to elders and affection to youngers was great. He never showed any disparity between his own brothers and half-brothers. When he was to select one of his four brothers to get enlivened, he chose Nakula leaving Bheema and Arjuna for the reason that elder son of Maadri should be the right choice to become alive when the eldest son of Kunthi was already alive. He loved even his evertroubling cousins, the Kouravas. Hence his epithet Ajaatjashatru.
He lamented a lot when Kunthi revealed that Karna was infact his elder brother. Not even the efforts of Vyaasa could not console him.
He was a great stragetist. During their exile in the forest, in Arjuna's absence, he undertook a long pilgrimage tour to be safe from possible enemy attacks. At the moment of beginning of the war, he could split Yuyuthsu from the other side. Also, he won over Shalya to discourage Karna. All the while he maintained cardial relations with Krishna, thus detaching his mighty and ferrocious half-brother Balaraama from his favourite disciple Duryodhana. All these strategies made his brothers' task of winning the war far easier.
He was considered highly learned too. His constant urge to gain knowledge was evident from his listening to the sages whether on the throne or in the forest. The way he answered the questions of Nahusha (as a python) and Yama (as a Yaksha) reveals his thorouh philosophical knowledge.
Scholars interpret that he was covertly cunning too. This is not far from truth. He did not even mind his wife's insult to keep from being identified in the year of incognito. He derided his beloved brother Arjuna himself when the latter could not kill Karna early. Though considered to be a man of no enemies, he terribly dreaded Karna and so heartily desired his death that he couldn't contain his joy at that news. He went to the battle field in person at night to see Karna's dead body to his own satisfaction. Also, the way he resorted to false methods and to lie to get Bheeshma and Drona killed was an undelible blemish to his character. Nor did he hesitate to kill Shalya himself in the war, despite his covert contribution to their victory. The only feeble excuse that can be offered was the grave circumstances.
He was surely cunning enough to be an able administrator of an empire but never was he known to have overriden the principles of righteousness.
After the war, he ruled the empire for thirty six years. Soon after learning Krishna's departure from this world, he decided to renounce the world. He walked off in renunciation along with his brothers and Droupadi. A dog from the city followed him since their starting. Beginning with Droupadi, all the others failed to maintain their yogic meditation and fell in the way one by one. He explained the reasons of fall of each of them to Bheema.
When he remained walking followed by the dog alone, Indra came to him and invited to mount the flier to go to heaven. But, Yudhishthira insisted that the faithfully following dog too must be allowed with him into the heaven. As Indra declared that dogs would not enter heaven, Yudhishthira was even prepared to forego the heaven itself.
The dog then disclosed its own form ie the form of the god Yama and announced to Yudhishthira that his commitment to virtue and righteousness was tested thus.
Thus tested, Yudhishthira was lead to the heaven where he could see duryodhana and others but not his brothers or Droupadi. On his request to see his brothers, Indra sent an angel to take Yudhishthira to the place where his brothers were. Finding out that all those including Karna were in horrible hell and his presence caused them a great relief , he prferred not to leave that place at all. All the gods were pleased with his selflessness and virtue. They disclosed to him that all that he saw was a purposeful delusion caused by the gods to test his character further. Thus thouroughly tested by the gods, Yudhishthira entered the heaven with his mortal body, which great echivement was praised by the sages. As advised by Naarada, he took a dip in the heavenly river Ganga and shed off all his mortal feelings and attachments. He finally coallisced with the god Yama whose incarnation he originally was.
His life stands high according to any stanards, despite some of his traits which look undesirable when seen from our present-day understanding.