What is Tax-free growth?
Tax-free growth means interest, dividends and gains earned inside an account are not taxed, and qualifying withdrawals are not taxed either. The money that goes in has usually been taxed already. TFSAs, ISAs and Roth accounts work broadly this way.
Why Tax-free growth matters
Over long periods the untaxed growth can be a large share of the final balance, so keeping it out of tax can matter more than the starting contribution.