Update is an english term and means "update" or "modernize". This word is often used to refer to newer versions of a certain technology, such as software, electronic games, etc..
Generally speaking, a update consists of update of information or data for something more recent and sophisticated. O update it can be done manually (via user command), or automatically (by the software's own initiative, which identifies available updates on your server, running the update).
The term update it is more used for small changes, such as minor updates and corrections, which are necessary modernizations for a better functioning of the product, without having to change it.
The applications of smartphones are an example of the type of product that suffers from updates constants.
See also: the meaning of software and Hardware.
Update and Upgrade
Update is only used for software such as computer programs when it comes to hardware (physical components of a device), such as the motherboard, the network card, the processors, etc., it is correct to say upgrade.
In this case, upgrade it also means "update to a more current version", but it usually occurs with changes in versions and technologies, that is, more often than not. updates.
Learn more about the meaning of Upgrade.