There are a few different field types, this article goes through each one by one.
Text
A text field is a field that you can type anything into. They are best used for fields that don't have clearly defined options, such as contact details.
Dropdown: single choice
These are for options where there is a clearly defined list of options, which people will only be one of.
Dropdown: multi choice
This is like a single choice, but people can select more than one option. This is good for times when you want people to be able to select more than one option.
Dropdown: with custom input
This allows you to have a dropdown, but also gives people the option to enter something if none of the categories fit their needs.
Number
This saves the answer as a number that can be added up in future analysis. This is useful for things like Household Size
Phone Number and Email
These are Phone Number and Email Fields. These fields check that what is entered is in the right format.
Postcode
This does a postcode lookup to help people type the full postcode.
Yes/No Checkbox
This is good for simple yes/no questions.
Date
This saves the answer as a date.