Easy, facile, simple, light, effortless, smooth are comparable when meaning not involving undue effort or difficulty (as in doing, making, giving, or understanding).
Easy is applicable both to persons and things that make demands for physical or mental effort or that impose a task upon a person and to the acts or activities involved in satisfying such demands or in accomplishing such a task.
Facile was once and to some extent is still used as a very close synonym of easy.
But it now chiefly applies to something which comes, or moves, or works, or gains its ends seemingly without effort or at call; it therefore is often used in derogation implying lack of constraint or restraint, undue haste, dexterity rather than meticulousness, or fluency with shallowness.
Simple stresses ease in apprehending or understanding; it implies freedom from complication, intricacy, elaboration, or other involvements which render a thing difficult to see through.
Light implies an opposition to heavy in nearly all of its senses, but in the one here considered it suggests freedom from burdensomeness or from exactions that make undue or difficult demands on one.
Effortless, though it carries many of the connotations characteristic of facile, suggests more the appearance of ease than actual absence of effort; often it implies mastery, skill, or artistry, and the attainment of such perfection that the movements or technique seem to involve no strain.
Smooth suggests an absence of, or the removal of, all difficulties or obstacles that makes a course or a career easy to follow or to pursue.