This is the 2588th most frequent Russian word.
столом
"Столом" means "by/with the table" (instrumental case of "стол," which means "table").
The word "столом" is in the instrumental case and is used to indicate the location where the action takes place (at the table).
Он сидел за столом.
He was sitting at the table.
Here, "столом" is also in the instrumental case, used to describe the surface over which something is placed (over the table).
Она накрыла на столом скатерть.
She laid a tablecloth over the table.
In this sentence, "столом" indicates the object under which the action occurs, showing spatial relationship (under the table).