In the beginning a lot of ecigs came with 3 pieces, the battery+atomizer+cartridge (with fabric in the cartridge to hold e-liquid). That setup never really wicked well and juice would get stuck in the cartridge and not feed to the atomizer.
Battery+Atomizer+Cartridge setup:
Most people now just replace the cartridge with a drip tip, which looks like this:
You place the drip tip ontop of the atomizer, it is just a mouthpiece with a center hole, which allows you to 'direct drip' and feed liquid directly onto the atomizer itself.
If you want lots of vapor and short inhales, low resistance atomizers 1.5-2.0ohm range produce tons of vapor when direct dripping (direct dripping 100%VG e-liquid is just insane vapor )