What are the specific differences between something being legal and decriminalized, especially if it is labeled as completely legal/decriminalized? What examples of this exist?
Decriminalization means that some action (e.g., drug consumption) is no longer considered a criminal action, which means that you're no longer sent to jail or get a criminal record. However, you may still face fines, confiscation of relevant goods and other consequences.
Legalization means that there are no legal repercussions for some action (e.g., drug consumption) whatsoever.
- Decriminalization versus Legalization of Marijuana (ThoughCo)
- The difference between decriminalisation and legalisation of sex work (New Statesman)
- The difference between legalisation and decriminalisation (The Economist, behind paywall)
- Decriminalization or Legalization? The Abortion Debate in Italy (Women & Criminal Justice)
- The Polygamy Question (Janet Bennion, Lisa Fishbayn Joffe)
It may be a situation where there are (almost) always a pair of offences being committed, and decriminalisation avoids the law actually assisting the party committing the more grave offence.
For example, if possession of, say, small amounts of marijuana for personal use is an offence, a person cannot go to the police (and still less testify on oath) concerning a drug dealer's behaviour, without incriminating himself. If possession is decriminalized, then he can.
Similarly if one decriminalizes prostitution (the act of selling sex for money or buying it), then it makes life harder for pimps.
In both cases the decision is a pragmatic one. The decriminalized thing remains illegal -- society does not approve of it -- but the law has decided that the best way to combat a criminal "industry" is to target the main players rather than their "customers" or the bottom rung of their orgainsation.
Caveat: IANAL and this is entirely dependent on jurisdiction.
In Australia, whether an offence is a crime or a misdemeanour is determined by its classification in the Criminal Code Act 1995 and subsequent amendments.
Conviction of any act classified as criminal goes on public record (literally, a criminal record) and this has far-reaching consequences including ineligibility for employment by the civil service at state and federal levels, and also for specified types of employment such as teaching and childcare.
After criminal conviction society will no longer trust you, whereas the consequence of a misdemeanour conviction ends with the fine. Punishment for crimes may involve mandatory imprisonment; this is not (so far as I can determine on a cursory reading) the case for misdemeanours, which normally offer a choice between payment of a fine and imprisonment.
A thing is completely legal if there is no conceivable legal obstruction.
Breathing is legal. Having a beach bonfire is not.