What does string mean in patricia tree wiki

Question

What does string mean in patricia tree wiki specifically here

Merkle Patricia trees provide a cryptographically authenticated data structure that can be used to store all (key, value) bindings, although for the scope of this paper we are restricting keys and values to strings (to remove this restriction, just use any serialization format for other data types).

They intend string as defined in the RLP wiki?

Note that in the context of the rest of this article, "string" will be used as a synonym for "a certain number of bytes of binary data"; no special encodings are used and no knowledge about the content of the strings is implied.

Answer 1

Different computers store binary data differently. The purpose of the RLP as stated in the referenced document is to

The purpose of RLP (Recursive Length Prefix) is to encode
arbitrarily nested arrays of binary data, and RLP is the 
main encoding method used to serialize objects in Ethereum.

In other words, it turns any binary data structure into a string that can be serialized on one machine and deserialized on another. I think, in this sense, in the first quote the word 'string' just refers to 'serializable' data.