Tantra means technique. Technique for the fulfillment of human desires. Fulfillment of desires leads to happiness. So tantra can be said to be a collection of techniques that leads to happiness. There are 2 types of happiness. 1) Temporary & 2) Permanent. Temporary happiness is the outcome of ordinary desires. This temporary happiness is called Kama as it is an outcome of ordinary desires. If the object of happiness is lost or if it becomes old then that happiness is lost. Then another desire comes in & the play continues.
In between if a desire comes in & when fulfilled the object of happiness is neither lost nor it becomes old, then no more desires comes in. This happiness is Permanent & is called Moksha.
So by the fulfillment of desires tantra gives both Kama (bhoga) & Moksha (yoga).