The Sanskrit word Vinyasa stems from the root word NYASA which means "to place" and the prefix VI, in this case, means "in a special way". This could refer to placing your arm in a special way while in triangle pose, or it could mean placing a sequence of postures in a special way to reach the desired result. For example, the desired result could be a sequence to help improve digestion, relieve back pain or reduce chronic fatigue. So Vinyasa can be flowing from one asana to the other, or flowing in your practice in a special way from asana, pranayama to meditation for a defined purpose. For example, - popular Vinyasa Yoga classes which mostly based on a set of sequenced asana practice for a particular theme.