Kevin up the forestays for no immediately obvious reason (unless he's getting out of somebody's way).
The larger, lower stay is the mainmast forestay, and the picture shows how the foresail hangs from it. The smaller, upper stay is the topmast forestay, which carries the staysail when the latter's in use, normally only in light breezes or when racing.
The big multi-pulley block is one of a pair that are use for raising and lowering the mast and gear at the beginning and end of the season or when going up-river under bridges.