Minecraft wiki entry for execute, associated text: Arguments
<pos>: block_pos
Position of a target block to test
It must be a block position composed of <x>, <y> and <z>, each of which must be an integer or a tilde and caret notation.
<block>: block_predicate
A valid block ID or block tag to test for
It must be in form of block_id[block_states]{data_tags}(accepts block tags), in which block states and data tags can be omitted when they are not needed.