Are cobwebs from spiders or dust?

Both Cobweb and Spider web refer to the silken threads spun by a spider. The meanings are identical.

However the Word "cobweb" can also be used to mean a single thread spun by a spider, whereas spider web tends to be used to describe a multi strand pattern.

On saying this, the actual definition defines both "cobweb" and "spider web" as being the same, with little or no difference between them.

A cobweb also refers to a web that is no longer in use by the spider that made it for what ever reason the spider has moved on.