This error message means you are attempting to input data of one type into a field that's expecting a different type.
The data type menu can tell you what types are available:
Some common data type errors are:
Attempting to use a boolean value as a string, i.e. setting the boolean value true to the string version of 'true' (the string version has quotation marks).
Attempting to use an ID as a number when it should be a string or vice versa.
Example: Stripe object IDs are strings
Charge objects in Stripe have IDs, but they are stored as strings, not as numbers.
Example: Hubspot object IDs are numbers
Company IDs in Hubspot are stored as numbers, not strings.