what does to say the rosary mean?

it's a set of (christian, pretty much catholic if you get technical) prayers. the beads of a rosary necklace are to help you keep track/walk trough the prayer cycle. I couldn't tell you the exact ones, but 'our father' is the 'long cycle', most repeated one, I believe.

To repeat a prayer for the number of beads in a rosary, which is a sort of necklace that is not really worn but just held in the hands while praying

Ask a Catholic. As a Christian it is not part of my Christian practice.

It's a Christian prayer that uses a rosary