In counting the omer, unify the name yud-kei with vav-kei in perfect unity what is the meaning “yud-kei”and :vav-kei”
One of the names of H-shem that we may not say is the name that spell Yud- Hey- Vav- Hey. In order not to mistakenly say the letters of that holy name, we substitute the letter Hey with Key, (really a “Kuf”, and not the letter “K”). What it actually means to “join the various parts of the Holy name together is very deep kabalah and beyond the scope of this site. The basic idea is that when we do mitzvos it has an effect in heaven, in a very lofty way.