grammar - 送ってくれた : Why is both "sending" and "giving" being used together here?

I encountered the sentence:

両親が私にはがきを送ってくれた。

I understand that: 送って translates to a verb meaning "to send", or I assume in this case "sending" due to the "te-form" being used.

I also understand that: くれた translates to a verb meaning "to give (to be given)"

So a literal translation of 両親が私にはがきを送ってくれた would mean:

My parents, to me, a postcard, Sending and given.

or..

My parents sent and gave me a postcard.

So I don't quite understand why you must say "they sent and gave me a postcard" instead of just "they sent me a postcard". For example

両親が私にはがきを送った。

Is there a grammatical/logical explanation for this? Or is this simply just how it's done for no reason?