A very simple PIR scheme on top of homomorphic encryption that supports multiplying with a plaintext and homomorphic addition, would look like this:

The client one-hot-encodes the query: Enc(0), Enc(1), Enc(0). The server has 3 values: x, y, z. Now the server computes: Enc(0) * x + Enc(1) * y + Enc(0) * z == Enc(y). Client can decrypt Enc(y) and get the value y. Server received three ciphertexts, but does not know which one of them was encryption of zero or one, because the multiplications and additions that the server did, never leak the underlying value.

This gives some intuition on how PIR works, actual schemes are more efficient.

[Disclosure: I work on the team responsible for the feature]