(We use parameter and option synonymously.)
Standard simulations in TeNPy can be defined by just set of options collected in a dictionary (possibly containing other parameter dictionaries). It can be convenient to represent these options in a [yaml] file, say parameters.yml, which might look like this:
Note that the default values and even the allowed/used option names often depend on other parameters. For example, the model_class parameter above given to a ~tenpy.simulations.Simulation selects a model class, and diffent model classes might have completely different parameters. This gives you freedom to define your own parameters when you implement a model, but it also makes it a little bit harder to keep track of allowed values.
In the TeNPy documentation, we use the Options sections of doc-strings to define parameters that are read out. Each documented parameter is attributed to one set of parameters, called "config", and managed in a ~tenpy.tools.params.Config class at runtime. The above example represents the config for a Simulation, with the model_params representing the config given as options to the model for initialization. Sometimes, there is also a structure of one config including the parameters from another one: For example, the generic parameters for time evolution algorithms, :cfgTimeEvolutionAlgorithm are included into the :cfgTEBDEngine config, similarly to the sub-classing used.
During runtime, the ~tenpy.tools.params.Config class logs the first use of any parameter (with DEBUG log-level, if the default is used, and with INFO log-level, if it is non-default). Moreover, the default is saved into the parameter dictionary. Hence, it will contain the full set of all used parameters, default and non-default, at the end of a simulation, e.g., in the sim_params of the results returned by tenpy.simulations.Simulation.run.
You can find a list of all the different configs in the cfg-config-index, and a list of all parameters in cfg-option-index.
If you add extra options to your configuration that TeNPy doesn't read out by the end of the simulation, it will issue a warning. Getting such a warnings is an indicator for a typo in your configuration, or an option being in the wrong config dictionary.