Paesi bassi vs. olanda
The Italian words 'Paesi Bassi' and 'Olanda' both refer to the Netherlands, but they have different scopes and usage in the Italian language.
Paesi Bassi
'Paesi Bassi' is the official Italian name for the Kingdom of the Netherlands. It literally translates to 'Low Countries' and refers to the entire country.
I Paesi Bassi sono famosi per i loro mulini a vento.
(The Netherlands is famous for its windmills.)
La capitale dei Paesi Bassi è Amsterdam.
(The capital of the Netherlands is Amsterdam.)
Olanda
'Olanda' traditionally refers to a specific region of the Netherlands, consisting of two provinces: North Holland and South Holland. However, it's often used colloquially to refer to the entire country.
Ho visitato l'Olanda l'estate scorsa.
(I visited Holland last summer.)
I tulipani dell'Olanda sono bellissimi.
(The tulips of Holland are beautiful.)
Summary
While 'Paesi Bassi' is the correct term for the entire country of the Netherlands, 'Olanda' is often used informally to mean the same thing, despite technically referring to only a part of the country. In formal or official contexts, 'Paesi Bassi' is preferred, but in everyday speech, both terms are commonly used interchangeably by Italian speakers.