ExpressionEngine channels are where your information gets stored. Within a channel you will typically find field. A field is a container that holds a specific type of information. For example, if you have a blog channel, you might have fields for the date, the title, the blog entry itself, an image, etc. Different field types let you manage your data intelligently. Collections of fields are stored in a Field Group. Each field group can be assigned to a channel.
ExpressionEngine has the following built-in fieldtypes: