At its core, a bong is a filtration device used for smoking cannabis, tabacco, or orther herbs. It typically consists of a bowl (slide), downstem, base, and mouthpiece.
Parts
-
MOUTHPIECE
Opening to inhale the smoke, usually found at the top of a bong. -
NECK
Connects the mouthpiece to the water chamber. -
SLIDE (aka BOWL)
The piece where you pack and burn your herb. -
JOINT
The opening where you insert the downstem. -
DOWNSTEM
A tube that connects the bowl to the water chamber and diffuses smoke through the water. -
WATER CHAMBER
The base and main water chamber of the bong.

Proper usage
1. Set water level.
Insert your downstem and fill the main water chamber with water. Tilt the bong if needed and make sure the holes in your downstem are completely covered. If there is a hole that's uncovered, most of the smoke will take the path of least resistance, and won't filter through the water. Keep the water level lower than the bottom of the bong joint, so it's less likely to spill. Adjust the level between these two points to your preference.

2. Pack bowl (slide).
Grind your herb of choice, pack the bowl, and slide it into the downstem. Evenly ground herb (not to a powder) ensures a consistent burn and is less likely to to create βcherriesβ that get sucked into the bong mid-hit.

3. Light bowl and inhale.
Put your lips to the mouth piece and light the bowl using a lighter, hemp wick, or a heat tool. You donβt need to hold the fire to the bowl. Light the herb and remove the fire.*Do not use matches, candles, zippos and other dirty sources. Youβll be inhaling their harmful byproducts.

4. Fill chamber
Milk the hit: As you inhale, smoking will begin filling the chamber(s) of the bong. Inhale slowly for the densest smoke and the most even burn.
Bongs are so smooth because they filter and cool down smoke. They do that in two ways: using the glass and the water.
Since the hot smoke generated from the burning bowl was literally just on fire, the heat gets transferred into the glass. The length of the neck of a bong can have a big impact. The bubbles created by the downstem cool and filter the smoke further. More bubbles mean more surface area for the smoke to touch.
Surface area is everything when it comes to bongs. Whether itβs more glass or more water, the more surfaces the smoke touches, the smoother the hit will beβup to a point.
5. Remove bowl, clear bong.
When youβre ready to clear the bong, pull out the bowl (slide), and inhale to clear all smoke. Donβt leave the smoke inside the bong too long or it will go stale and taste bad.