A crafter is a Character that makes stuff like Weapons, Armor, Ammo, Drugs, tools and explosives. In the past, when there was a Level Cap, it was treated like a character class, and players often had a crafting alt with a crafting build.
Nowadays though, on FOnline: Reloaded every character can be a crafter since there is no level cap on Skill Points and there are skill books which increase some skills. When players still have a designated crafter alt, it is popular to make a mule character with high ST since they can carry more raw materials at one time, and with high IN they can have a high number of Skill Points in Repair, Science, Traps and Doctor even at low Levels.
However, all that is needed for any character, even a fighter, to craft tier 2 gear is Repair 100. This is easy to reach, especially with Skill Books, so a more popular approach to crafting is not to have a single dedicated alt anymore. Instead, use a fighter. Get his Repair to 100, pay 4500 Caps for professional training, eat some Blueprints, and start working the Gun Runners Caravan Package quest. This gets access to the Gunrunners Advanced Workbench, where any fighter will benefit from all that delicious crafting XP, and thus get to higher levels.