“Tera” is used to distinguish between a Buddhist temple and a Shinto shrine. It can also be read as “dera” depending on how it’s written. It’s Sino-Japanese pronunciation is “ji”.
Meaning: breath, energy, spirit
Japanese people will ask each other “元気ですか？／Genki desu ka?” They are asking after the other person’s feelings, energy, or general health. It’s simply polite to respond “元気です。/Genki desu. /I am well,” even if you are not doing well at all. The phrase is a mere courtesy, unless you’re talking with someone you are close to.