Canal

A communication channel or transmission channel is a medium (physical or not) that allows the transmission of a message (or more generally information ) , from a source (or sender) to a recipient (or receiver).

Source: Wikipedia

In practice, we tend to confuse the medium and the message. For example, in 'I received an email ', the word email refers both to the transmission channel and to the message itself.

In Martech platforms, the concept of a channel typically appears across several interfaces: 
– when creating a campaign, to determine the message sending channel,
– when configuring the fields of a Single Contact Record (SCR), to determine if a contact has an address for a specific channel (email address, postal address, mobile number for sending SMS messages, etc.),

So-called "omnichannel" marketing platforms allow messages to be sent across all types of channels: email, SMS, print, mobile wallet, social networks, fax, push notifications on apps, etc.
This makes it an ideal tool for staying in touch with customers and prospects…
This is referred to as omnichannel.