Red Box

Race as Class and other differences
If you discovered the hobby in the 1980s or maybe the early '90s chances are it was through the Red Box. Red Box is the 1983 version of the Basic Rules. The first Basic Set was written by J. Eric Holmes and saw publication in 1977. Dr. Holmes' Basic came out before AD&D and was an effort to make the three LLBs more accessible to folks with little or no wargaming background. Despite some inconsistencies, I think it was a good idea and a good game...although it only covers character levels 1-3. By 1977 Gary Gygax and TSR had decided to split their fantasy RPG line of products calling one Advanced (AD&D), the other Basic/Expert (D&D). White Box would be retired in the process. Mr. Gygax would devote much of his future time to writing the Advanced books.
As a result of this "split" and other later edition decisions, D&D has really become more than one game. Like many who started with White Box, I tend to adapt the later versions to fit into my preferred way of running the game, so I say everything I referee has a good dose of White Box. This is definitely true of the way I used Red Box. The Red Box and other boxes in the product line, Blue Box (Expert), Green Box (Companion), Black Box (Master) and Gold Box (Immortals), had good production quality and featured illustrations by Larry Elmore that make them very attractive, even today as collector items. The Red Box gave a good explanation of the basic rule mechanics and idea of roleplaying and was an easy intro game for new players. I refereed many a game in the '80s and 90's using Red Box with my White Box alterations. In 1991 the color boxes (not Gold) were brought together in one hard cover volume called the Rules Cyclopedia, which I still occasionally have at my table.
Red Box included some significant rule differences (from White Box or the Advanced game) which have come to be associated with the Basic/Expert rules in general, such as race as class. In Red Box it is possible to play one of several classes if the character is a human- cleric, fighter, magic-user or thief being the basic choices. The traditional elf, dwarf and halfling are also available as player character races, now called demihumans and each is its own class. Level limits still exist as compensation for the demihuman racial advantages (such as improved vision), but  generally top-out at higher level than in White Box. I think race-as-class makes some sense if the campaign is highly humanocentric with the occasional non-human. 
In 2000, Wizards of the Coast brought the two D&D lines together, dropping the name "Advanced" and released their 3rd Edition game, which differed significantly from all previous versions. Red Box, like White Box before, entered the realm of "games of yore". They still fetch a nice price on the secondary market and I assume Red Box, like White Box, still has a following.