1800 Reposado Tequila is a mid-range premium tequila, produced from 100% blue agave and aged for six months in French and American oak. It's decently complex, with notes of dried fruit and grass, as well as a hit of smoke.
1800 Tequila is a brand owned by Casa Cuervo, producers of the world-famous Jose Cuervo line of tequilas. According to their marketing materials, the name refers to the year tequila was first produced (this doesn't appear to be even remotely true), and the 100% blue agave product is branded as a more premium tequila than others in the family. The 1800 range includes the standard blanco, reposado, and añejo, as well as a coconut tequila and a handful of specialty extra-añejo bottles.