and; moreover; at the same time — a conjunction/adverb used in more formal or written Japanese to add or combine facts
彼は有能で、かつ人柄も良い。
He is capable and, at the same time, has a good character.
政策は実現可能で、かつ費用対効果が高くなければならない。
The policy must be feasible and also cost-effective.
彼女は演技が巧みで、かつ歌も上手だ。
She is skilled at acting and also good at singing.