Updated: Feb 29, 2020
The terms "Waza" and "Kihon" are essential elements in Iaido practice.
"Waza" refers to a set of pre-defined moves. There are various sets of wazas, each requiring understanding and competency in specific skills. For example, Seiza no bu, Batouho no Bu, etc.
"Kihon" refers to basics. Examples of these are form of posture (kamae), tenouchi, sheathing (noto), cutting-line (hasuji), etc.
The 2 supports each other. Indeed, the kanji character of "Waza" (わざ) is [技], lit. "skill"; or finesse of the waza thereof. It goes without saying the more one practices specific waza, the better one is in that waza. However, the essential distinction in doing a waza and doing good wazas lies in kihon.
The kanji of "Kihon" (きほん) is [基本], lit. "basics"; the fundamental basics. These are the elements that make up the wazas. Improving one's kihon makes current learnt wazas better, & sets the foundation for easier learning and internalization of new wazas. An analogy would be "Kihon" as bricks, "Wazas" as type of architecture. Synergy of waza and kihon paves the way for more advanced wazas.
What does these mean to an iaidoka? When learning new wazas, it is not expected to be able to do the wazas perfectly with the finesse as that of the Sensei or seniors. Rather, strive to do the wazas with correct form in one's practice first. Understand how to apply and piece together the kihon at various stages in a waza.