I'm currently taking my first tax course in University, and boy is it confusing (especially for an international student)!

I'm having trouble understanding CDA and RDTOH accounts.

My interpretation of CDA account is a cumulation of the non-taxable portion of any capital gains that a private corporation realizes, and that whatever this amount is can be used to pay out dividends?

My interpretation of RDTOH is an amount that's refundable back to the corporation when dividends are paid to shareholders, and that the corporation would get $1 of refund for every $3 of dividend paid out? So basically if a corporation had $5000 in its RDTOH account, the corporation would get a $5000 refund if it issued $15000 in dividends?

Could anyone clarify these two accounts up for me? The textbook isn't very clear at all, thanks in advance!