What is a Praying at a shrine (参拝（二拝二拍手一拝）)?

参拝（二拝二拍手一拝）Praying at a shrine (two bows, two claps, one bow)

At most shrines, visitors bow twice, clap twice, pray, and bow once more. Everyone is welcome to pray.

The basic sequence at most shrines today is two bows, two claps, one bow.
The two-bows-two-claps rule for ordinary visitors is a postwar development; it began as a priests' protocol in the Meiji era and spread after the Association of Shinto Shrines recommended it.
At Izumo Taisha, worshippers bow twice, clap four times and bow once.
Ise's priestly style (hachidohai) uses eight claps.
If there is a bell, visitors ring it gently before praying.
There is no fixed amount for the offering; the act of reverence matters.
Visitors bow at the torii and walk at the side of the approach, as the centre is for the kami.
At Buddhist temples there is no clapping; people press their palms together (gasshō) and pray quietly.
伝 legend A 5-yen coin is popular because go-en sounds like a word for a connection.