How do taxes work with gained (not bought) Bitcoin?

Let's say I buy some Bitcoin on a US exchange and transferred it to an overseas investment firm and made some gains which are paid in Bitcoin. If those gains stay there or are moved to a personal hard wallet that I own, are they taxable or do I need to report them at all? I can't seem to find much information about this.. I've been thinking that it wouldn't be taxable until I move the extra Bitcoin to the exchange and sell it for cash. My reasoning is that it's considered property and if someone gives me something I didn't have before I'm not taxed on the value of the item until I sell it and make some money off it. Thoughts?

Also when it is sold and taxed, is it income or capital gains?