What is the difference between sacraments and sacramentals?

Simply put Sacramentals are things or actions that are used to show respect or love of God while Sacraments are rites where God acts directly on the person. However, if you need more specifics then:

Sacramentals are material objects, things or actions (sacramentalia) set apart or blessed by the Roman Catholic Church, the Orthodox Churches, the Anglican Churches, and Old Catholic Churches to manifest the respect due to the Sacraments, and so to excite good thoughts and to increase devotion, and through these movements of the heart to remit venial sin, according to the Council of Trent (Session XXII, 15).

Examples of rituals that are sacramentals are making the sign of the cross, bowing the head, genuflection, prostration, the imposition of blessed ashes (the ashes themselves are also a sacramental).

Other examples of objects that may be considered sacramentals are holy water, ashes, bells (especially church bells), blessed fire, blessed salt, candles, the nativity scene, the Advent wreath, crucifixes, holy oil, holy water, incense, liturgical vessels (e.g. chalices), a Mary garden, medals (e.g. the Miraculous Medal or the Saint Benedict Medal), palm branches, graves, funeral palls, religious habits and scapulars, rosaries, vestments, or wedding rings.

A sacrament, as defined in Hexam's Concise Dictionary of Religion is what Roman Catholics believe to be "a rite in which God is uniquely active.

The following are the Seven Sacraments of the Catholic Church:
  • Baptism (Christening)
  • Confirmation (Chrismation)
  • Holy Eucharist (or Holy Communion)
  • Penance (Confession)
  • Anointing of the Sick (known prior to Vatican II as Extreme Unction (or more literally from Latin: Last Anointing); informally, the "Last Rites")
  • Holy Orders
  • Matrimony