Concepts similar to the Trojan horse
The Trojan horse should not be confused with other related notions:
The injector (or dropper) is almost identical to the horse, because it also serves as a vehicle for malicious intent. But the injector is a program specially designed to spread parasites, while the horse is a modified version of an existing and legitimate program.
The backdoor is a program that will run discreetly on the computer where it is installed to create a security vulnerability. The backdoor opens one or more ports on the machine, allowing it to access the Internet freely and download a parasite without the user's knowledge. The backdoor is therefore not a Trojan horse: it does not carry the parasite in it, it will simply open access and retrieve, via the Internet, the malicious program that is on a remote server.
The RAT (Remote administration tool) is a software for remote control of a computer. A RAT can be a legitimate tool (for example, for remote troubleshooting), but it can also be used by a hacker to grab a machine. In this case, the introduction of the RAT on the machine to be controlled is done without the user's knowledge. For example, by a Trojan horse that contains the RAT, but the RAT is not the horse. Contrary to what we sometimes read, the T of RAT does not mean Trojan but Tool.
Decompression bombs do not carry parasites, but they can be confused with Trojans because the notion of container also comes into play. It is a compressed file, for example a zip file, of reasonable size until it is opened. But when the user tries to decompress it, it will generate a file of a gigantic size. This "explosion" causes the computer to slow down or crash, and saturates the hard disk with unnecessary data. Although these are malicious containers, the operation of decompression bombs has nothing to do with the operation of Trojan horses. Indeed, they do not carry any independent parasites, they saturate the machine with random data.
The Trojan Stealer, rather specialized in data theft and especially online accounts (Mail, Social Networks or even banking). The prefix used by antivirus software can then be Trojan.PWD where PWD stands for password for password.