There are several different custom field types available, each with a different purpose.
A text field is designed for a single line of data, such as a name.
A text area field is designed for multiple lines of data, such as a full address, or a long note.
A checkbox field is designed for yes/no or true/false type values.
A selectbox field is designed for selecting a single option from a pre-populated list of options.
A multiple selectbox is designed for selecting multiple options from a pre-populated list of options.
A date field is designed for capturing a single date.