Hi gamma
When you invest in a company, you will often share in the profits through a dividend. When you buy a bond/gilt, you will receive a percentage of the amount of the bond you purchased bianually. So, what you said is true.
However, just to clarify, if you look only at capital gain through price change (i.e. ignore dividends, interest payments, etc), then any gains made will be made at the expense of the party(ies) that traded the opposite side to you. So on a purely transactional basis, trading is a zero sum game (actually, it's negative sum with respect to the leeching from broker comissions, exchange fees, etc). It just depends on what factors you include or remove from the arguement.