Liquor is produced by distilling fermented grain, fruit, or vegetables. This excludes beverages like beer and wine, which are fermented but not distilled.
Liquors typically have no added sugar. Liquors with added sugar and flavorings are known as liqueurs. Grand Marnier, Frangelico, etc. are liqueurs.
All home and professional bar setups are centered around a core group of liquors known as the "well". These are:
No bar is complete without these core liquors in some variation. If you do not have them, you do not have a bar, end of story.