The two words canal and channel are similar and dissimilar in meaning, usage and intent. A canal can be a channel and a channel can be a canal, when you use these words to describe openings, through which water or a another liquid may flow or be contained for instance.
A canal can be a strip of water, usually narrow and long body of water, through which boats can navigate or it can be for the purpose of irragation. A canal can be an inland, body of water, in which the levels are controlled by a set of locks. Canals as bodies of water usually open into a river or sea. A canal can be natural, built by normal erosion of land or artificial, which means it is man-made such as the Suez Canel.
A channel is the bed of a stream or river, or it can be the deepest part of a river or harbor. A channel can be a strait, a narrow body of water connecting two seas. A channel can be a pipe or a pipelike structure used as conduit. Channels can also be a pathway, through which information flows, such as a CEO notifies an officer and then the message passes from one level of emplyees until it reaches those on the lowest level.
In communications a channel can be gestures, actions, sounds the spoken, sign or written messages to others. In electronics a channel is a frequency band used to transmit and receives information by way of electromagnetic signals for instance in television. In computers it is network, through which conversation can happen in real time, a group of people can carry on a conversation at one time. A channel can be the person or medium or spirit guide. And, a channel can be the opening within a cell membrane, through which molecules and ions pass in and out of the cell. There are many channels within the human body, and there are also many canals.
Addtional information about canal and channel can be found in any dictionary or enclyclopedia.