It means individual humans living in a State which does not specifically claim power over a particular set of actions can freely choose their own behaviors in that regard.

Is regulation of dancing with wildlife delegated to the United States?

No.

Is regulation of dancing with wildlife prohibited to the States themselves?

No; a State could decide to regulate dancing with wildlife.

Does your State regulate or prohibit dancing with wildlife?

If not, YOU GET TO CHOOSE whether to dance with the raccoons or other wildlife you encounter, and if you actually dance, you get to do so any damn way you please.

EDIT: Article 1, Section 8 of the Constitution is generally considered the nuclear option for preventing The People or even the individual States from exercising their own judgement in anything covered by the 10th Amendment:

Section 8: Powers of Congress The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States; [bold added]

In other words, if anyone claims a particular action might possibly impact the "general welfare", as defined (if at all) by the person making the claim, the 10th Amendment does NOT apply in that situation and the Federal government can do whatever it deems necessary to make people behave as the Federal government wants them to.

Henry David Thoreau's comment on this whole mess [again, bold added]:

I heartily accept the motto, "That government is best which governs least"; and I should like to see it acted up to more rapidly and systematically. Carried out, it finally amounts to this, which also I believe--"That government is best which governs not at all"; and when men are prepared for it, that will be the kind of government which they will have. Government is at best but an expedient; but most governments are usually, and all governments are sometimes, inexpedient. The objections which have been brought against a standing army, and they are many and weighty, and deserve to prevail, may also at last be brought against a standing government.