Explorers are the original classes of MapleStory. These are the main branches of Maplers who fought in the general effort against the Black Mage and his horde of evil monsters. Later, Cygnus Knights and the Heroes, joined the Explorers to lead the battle against the Black Mage. Explorers are given their own storyline in RED.
Beginner is a character class in MapleStory. All new players who are in the category of Explorers start the game as Beginners on Maple Island. At level 8 or 10 (depends on the job), Beginners may make the first job advancement and become either a Warrior, Magician, Bowman, Thief, or a Pirate. The game recommends Beginners to make the advancement to a Magician at Level 8, and Level 10 for the other first job advancements. Though Beginners are not considered one of the "main" character classes, some people choose to remain as a Beginner past the first, second, or even third job advancements. They do this for a variety of reasons, the main one being that it is a challenge to take a Beginner that far.
Permanent Beginners, also known as Perma-Beginners, are Beginners who choose not to make a job advancement. They get several perks, including cheaper taxi rides, no EXP-loss upon death, and plenty of respect after reaching a certain level. However, disadvantages to being a Perma-Beginner include having less HP and MP (Health and Mana Points), lack of skills, and very limited access to equipment. Their build is similar to that of a Warrior's so they rely mostly on melee weapons, but they will also never hit as high as most Warriors. It is hard to level up as a Perma-Beginner since a majority of quests are job-restricted, and it is harder to take down most monsters than other characters. Nonetheless, plenty of players are proud to be Beginners.