Signal is an electrical or electromagnetic current that is used for carrying data from one device or network to another.
In signal processing, a signal is a function that conveys information about a phenomenon. In electronics and telecommunications, it refers to any time varying voltage, current or electromagnetic wave that carries information. A signal may also be defined as an observable change in a quality such as quantity.
Signal is an encrypted app that lets you send messages and make calls via the Internet. Signal's USP is its focus on privacy. It supports group chats and group video calls too. Signal is open source and its code is peer-reviewed, which means that its privacy and security is regularly checked by independent experts.