When I read the document:
When the client next requests the same resource, it might send along a header such as either
If-modified-sinceorIf-unmodified-since, containing the date of the last modification time it was sent.
I saw there are send along here, I know its meaning. but you know, we can use send directly, why there is more – an along here?
What's the difference between send along and send?
A meaning of along is "additionally" or "extra" in the sense of delivering something else other than what was expected.
Along is used because not only is the requested resource being sent (that's implied in the sentence), but also a header. If along did not appear in the sentence, it could mean the header was sent instead of the resource.
Send X along where X is a person and there is nothing specified for along can mean "to dismiss," but this is not what is meant here.
