What is a search term?
A search term is entered into a search engine to conduct a search. It could be a string of words or in the form of a question.
What is a key phrase?

On web pages, the words we write that help customers find a website are known as keywords. So what is a key phrase? Keywords make up key phrases.
Organic SEO versus paid search results
Businesses realise the importance of maintaining a strong presence in search engine results pages (SERPs).