The full deposit of faith was given to the Church by Jesus in the form of Scripture and Tradition. This means that the Gospel of Christ exists in both written (Scripture) and oral (Tradition) form. Here is the difference. Tradition, sometimes referred to as Sacred Tradition (Always with a capital “T”) is the oral teachings of the apostles. It is just as important, and just as inspired as the written word. St. Paul mentions the importance of it several times:
2 Thes 2:15 "So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter. "
2 Thes 3:6 “Now we command you, brethren, in the name of our Lord Jesus Christ, that you keep away from any brother who is living in idleness and not in accord with the tradition that you received from us.”
1 Cor 11:2 "I commend you because you remember me in everything and maintain the traditions even as I have delivered them to you. "
2 Tim 3:14-15 “But as for you, *continue in what you have learned and have firmly believed, knowing from whom you learned it, and how from childhood you have been acquainted with the sacred writings *which are able to instruct you for salvation through faith in Christ Jesus.” (Note that this passage does not contain the word traditions, but describes what Tradition is, “Continue in what you have learned, knowing from whom you learned it.”)
This last passage clearly shows that oral tradition is just as important as scripture.
However, traditions (small “t”) are mearly customs developed by men. Christ does not condemn ALL traditions, just ones that make a mockery of the Law.
Matt 15: 2-3 “Why do your disciples transgress the tradition of the elders? For they do not wash their hands when they eat.” He answered them, “And why do you transgress the commandment of God for the sake of your tradition?” **Mark 7:10-13 ** “For Moses said, ‘Honor your father and your mother’; and, ‘He who speaks evil of father or mother, let him surely die’; but you say, ‘If a man tells his father or his mother, What you would have gained from me is Corban’ (that is, given to God) – then you no longer permit him to do anything for his father or mother, thus making void the word of God through your tradition which you hand on. And many such things you do.”
Plus think about it, everything that the apostles learned from Jesus, they learned by Tradition. Jesus did not sit down with them with books and teach them. He taught them about the Gospel and the Kingdom of Heaven orally. How many times do you hear Jesus quote scripture when he is instructing the apostles? None! That is because his oral Word is just as inspired as the written one. Jesus never commanded the apostle to go print books, he commanded them to make disciples and teach them to obey God. 2000 years ago, the most commonly accepted form of teaching was oral instruction.