Manual - the value you'll assign for 'Parameter value' field will be used as is.

Environmnet - the value you'll assign for 'Parameter value' will be looked for in the environment parameters and the resolved value will be used. If you named your parameter 'my_parameter' put here 'my_parameter' (exactly the same value).

From JSON - the value you'll assign for 'Parameter value' will be looked for in the JSON file you specified for the 'Path to JSON file' entry.