What is the purpose of xml: base

Good afternoon,

I'm programming an xml and I'm still very new to this programming, and one of the tags I found looking at some examples was:

<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:rdfs="http://www.w3.org/1999/01/rdf"
xmlns:base="http://www.animais.org/animais">

But I could not distinguish it, can you help me?

Thank you in advance.