Freebasing is a term used in connection with recreational drugs.
It means that you are smoking a drug, rather than snorting, ingesting, inserting or shooting it.
Most drugs, especially party drugs, are found in its salt-form, making them water soluble, so that your body can absorb them, followed by you getting high.
However, freebase drugs are drugs in their non-salt form, and they are not water soluble, and cannot simply be absorbed by your body.
The common party drug cocaine is in a salt form, therefore, not freebase, and it can be snorted to feel effects.
However, its freebase version is crack cocaine, which is not water soluble, and must be inhaled or smoked to get you high. It does not give you any effect if you ingest it or snort it.
People in USA first started smoking cocaine instead of snorting it in 1974, and it was mostly done in California.
It is called freebase because the compound being smoked is the conjugate base of the original drug – which is a salt.
The term is used by people who regularly do drugs.
Various sources state that the drug has higher purity when being freebase, but others state that it is a myth.
Some drug users prefer to smoke or inhale the drug as it kicks in faster, but the high is also shorter.