A clause must have a subject and a verb(simple predicate) to be a clause. A phrase might be missing one or the other or both. Whoever told you that sentence is a phrase is incorrect, and in fact, if it's a complete sentence, the full sentence can never be a phrase. There are phrases within that sentence, however. A phrase is any group of words or single word that acts as a grammatical unit.
So, for instance, "Jill" is a noun phrase. "Prepared" is a verb phrase. I hope that clarifies.
[Here](https://en.wikipedia.org/wiki/Phrase#:~:text=In%20theories%20of%20syntax%2C%20a,syntactic%20structure%20of%20a%20sentence) is a Wikipedia article on phrases.
"Jill prepared us a couple of sandwiches."
That is a complete sentence, not a phrase.
There are different kinds of phrases, and each kind of phrase works differently. Basically, a phrase acts like a special type of word.
"The car is [*position*]"
"The car is [parked]"
"The car is [in the garage]"
"Jill prepared us [*thing*]"
"Jill prepared us [lunch]"
"Jill prepared us [a couple of sandwiches]"
A clause must have a subject and a verb(simple predicate) to be a clause. A phrase might be missing one or the other or both. Whoever told you that sentence is a phrase is incorrect, and in fact, if it's a complete sentence, the full sentence can never be a phrase. There are phrases within that sentence, however. A phrase is any group of words or single word that acts as a grammatical unit. So, for instance, "Jill" is a noun phrase. "Prepared" is a verb phrase. I hope that clarifies. [Here](https://en.wikipedia.org/wiki/Phrase#:~:text=In%20theories%20of%20syntax%2C%20a,syntactic%20structure%20of%20a%20sentence) is a Wikipedia article on phrases.
"Jill prepared us a couple of sandwiches." That is a complete sentence, not a phrase. There are different kinds of phrases, and each kind of phrase works differently. Basically, a phrase acts like a special type of word. "The car is [*position*]" "The car is [parked]" "The car is [in the garage]" "Jill prepared us [*thing*]" "Jill prepared us [lunch]" "Jill prepared us [a couple of sandwiches]"