Although the terms are often used together, "ecumenical" technically only concerns "Christian unity" while "interfaith" (or interreligious) concerns relations with non-Christian faiths. Judaism, however, holds a unique place, as we are the descendants of the Jewish faith tradition upon which Christianity was built and thus may consider our relations as “ecumenical.”
The search for Christian unity was one of the principal concerns of the Second Vatican Council. Vatican II published the “Ecumenical Directory" with the purpose of coordinating and developing the ecumenical efforts of the Church. The Catechism of the Catholic Church (1992 ed.) includes the ecumenical dimensions part of the basic teaching for all the faithful of the Church.
There are some misconceptions concerning ecumenism (and interreligious dialogue,) some unintentional, some deliberate. Ecumenical dialogue “implies speaking and listening, giving and receiving, mutual growth and enrichment. It is based on witness to one’s faith as well as openness to the religion of another. It is not a betrayal of the mission of the Church, nor is it a new method of conversion to Christianity.” (Pontifical Council for Interreligious Dialogue)
Jesus prayed, "That they all may be one." (Jn 17:21). The Second Vatican Council (“Vatican II”) directs the Church Faithful to this end.
Judaism, Islam, and Christianity are called “the Abrahamic religions” because they all share in their declaration of being descendants of Abraham.