Options.get and store

In Clang-tidy Check,

FunctionSizeCheck::FunctionSizeCheck(StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      ParameterThreshold(Options.get("ParameterThreshold", -1U)),
 {}

void FunctionSizeCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "ParameterThreshold", ParameterThreshold);
}

Options.get(“ParameterThreshold”, -1U) it means we can get value from clang-tidy and assgined to ParameterThreshold?
and Options.store(Opts, “ParameterThreshold”, ParameterThreshold)? store value of ParameterThreshold to ParameterThreshold in .clang-tidy?

Yes.
Options.store is used by --dump-config option.
And code that you showing is old, as now optional types are ± supported and used by this check.