Garment Worn Always
The LDS garment is worn under regular clothing, both night and day, and is only to be removed for specific activities such as swimming, sports, etc and should be replaced as soon as possible.
The Garment is a Symbol
Wearing the garment is a symbol of our covenants made with the Lord.
"The white garment symbolizes purity and helps assure modesty and respect for the attributes of God" ("What are Latter-day Saint Garments?," LDS FAQs, BYU Studies).One way the garment can be seen as a symbol is how Paul taught to take upon us the whole armor of God (see Eph. 6:13 and D&C 27:15). Wearing the garment is an outward expression of an inward covenant.
The Garment is a Sacred Blessings
Wearing of the LDS garment brings blessings to those who worthily and faithfully keep the covenants they have made in the temple.
"Once people are endowed, they have the blessing of wearing the temple garment throughout their lives. They are obligated to wear it according to the instructions given in the endowment. Those who have been endowed in the temple must remember that the blessings that are related to this sacred privilege depend on their worthiness and their faithfulness in keeping temple covenants" ("Gospel Topic: Temples," Wearing the Temple Garment, LDS.org.)
The Garment Should be Respected
As stated in the quote below, the LDS garment is to be treated with respect, not shown to others who do not understand it, and not modified in any way.
"The garment provides a constant reminder of the covenants made in the temple. The garment should be treated with respect at all times. It should not be exposed to the view of those who do not understand its significance, and it should not be adjusted to accommodate different styles of clothing. When worn properly, the garment provides protection against temptation and evil. Wearing the garment is an outward expression of an inward commitment to follow the Savior" ("Gospel Topic: Temples," Wearing the Temple Garment, LDS.org.)
Modest Clothing Should be Worn
When wearing the garment modest clothing should be worn over this sacred Mormon underwear, and should thoroughly cover it. In the official manual from the Church of Jesus Christ of Latter-day Saints, "Preparing to Enter the Holy Temple," it states:
"The wearing of such a garment does not prevent members from dressing in the fashionable clothing generally worn in the nations of the world. Only clothing that is immodest or extreme in style would be incompatible with wearing the garment. Any member of the Church, whether he or she has been to the temple or not, would in proper spirit want to avoid extreme or revealing fashions" (Preparing to Enter the Holy Temple, 1.)
Ancient History of the Garment
The practice of wearing a holy piece of clothing is not a new concept, nor is wearing of the sacred garment new- it has an ancient, scriptural history:
"It should be understood that 'the things of the Lord' (2 Ne. 4:16) have included sacred clothing from the very beginning of this world. The scriptures contain many references to the wearing of special garments by the ancients. Prior to their expulsion from the Garden of Eden, Adam and Eve were clad in sacred clothing. We read: 'Unto Adam also and to his wife did the Lord God make coats of skins, and clothed them' (Gen. 3:21)....
"Moses was commanded to place holy garments and priestly vestments upon Aaron and others, thus preparing them to officiate in the tabernacle. Said the Lord to Moses, 'And take thou unto thee Aaron thy brother, and his sons with him, from among the children of Israel … and thou shalt make holy garments for Aaron thy brother for glory and for beauty... that he may minister unto me in the priest's office' (Ex. 28:1–3)" ("The Temple Garment: 'An Outward Expression of an Inward Commitment,'" Elder Carlos E. Asay, Ensign, Aug 1997, 19.)
New Testament Refers to Being Endowed
John W. Welch explained the meaning of the Greek word Enduo/Endued/Endowed:
"What is the meaning of the word endued or endowed? In Luke 24:49, shortly after his resurrection, Jesus told his Apostles, 'I send the promise of my Father upon you,' but they were to remain in Jerusalem, 'until ye be endued with power from on high.' (Emphasis added; see also Acts 1:4–5, 8.) The Greek word in the text is enduo.
"Webster's American Dictionary of the English Language (published in 1828) noted that the English word endue (or indue) 'coincides nearly in signification with endow, that is, to put on, to furnish... to put on something; to invest; to clothe.' The Compact Edition of the Oxford English Dictionary notes that endue means 'to put on as a garment; to clothe or cover.' Indeed, Joseph Smith’s diary uses the spellings endument and endowment interchangeably, as when he prayed in December 1835 that all the elders might 'receive an endument, in thy house.'
"The Greek word enduo has two main meanings. The first is 'to dress, to clothe someone,' or 'to clothe oneself in, to put on.' Second, the word can also be used figuratively, meaning to take on 'characteristics, virtues, intentions.'
"Thus, the endowment is a dressing not in ordinary clothes, but 'with power from on high' (Luke 24:49) and in the virtues and intentions of God. It involves the opportunity to 'put on [enedusasthe] Christ' (Gal. 3:27), so that 'this mortal [can] put on [endusasthai] immortality.' (1 Cor. 15:53.) It is possible to see both literal and figurative significance in the word enduo in connection with the desire of the pure in heart to be encircled in the robes of God’s righteousness" ("New Testament Word Studies, Ensign, April 1993, pp. 28-30.)
Thus one could say that the garment is a type of Mormon underwear although as members of the Church of Jesus Christ we sacredly refer to them as garments.
For additional articles on this sacred Mormon underwear, the garment, please see the Temple Gospel Topic at LDS.org as well as the links under "Elsewhere on the Web."