sur·ro·gateSo, if you don't know already, a surrogate carries and delivers a child for an intended parent or parents to raise.
a substitute, especially a person deputizing for another in a specific role or office.
"she was regarded as the surrogate for the governor during his final illness"
synonyms: substitute, proxy, replacement
A surrogate comes in two basic forms: a traditional surrogate (TS) or a gestational surrogate (GS).
A traditional surrogate uses her own eggs and a gestational surrogate doesn't. This is the most basic of descriptions.