Efficacious grace is the actual, effective grace, for the Church affirms de fide (of faith) that no act conducive to salvation can be performed without grace, which causes us to act for our salvation.
As we can read in Ezekiel, “I will put my spirit within you and make you live by my statues, careful to observe my decrees” (36:37).
The grace that causes us to act is efficacious, effective in producing the good actions through our will concurring with the grace. Although efficacious grace is conferred, it is not the only kind of grace.
Efficacious grace is the grace by which the hard heart is overcome and we yield to act, aided in our will by the efficacious forces of the grace.
Other forms of grace can be classified for understanding with terms such as sanctifying, actual, habitual, sacramental and sufficient.
Grace, in general, is a supernatural gift of God to intellectual creatures (i.e. human, angels) for their eternal salvation.
Grace plays the part of the means, indispensable and divinely ordained, to effect the redemption from sin through Christ and to lead humankind to their eternal destiny in heaven. (9:50)