Países bajos vs. holanda
The Spanish words 'Países Bajos' and 'Holanda' both refer to the same country, but they have different scopes and usage in the Spanish language.
Países Bajos
'Países Bajos' is the official Spanish name for the Netherlands. It refers to the entire country, including all its provinces and territories.
Los 'Países Bajos' son famosos por sus tulipanes y molinos de viento.
(The Netherlands is famous for its tulips and windmills.)
El equipo de fútbol de los 'Países Bajos' ganó el partido.
(The Netherlands national football team won the match.)
Holanda
'Holanda' technically refers only to two provinces in the Netherlands: North Holland and South Holland. However, it's often used informally to refer to the entire country.
Muchos turistas visitan 'Holanda' para ver los campos de tulipanes.
(Many tourists visit Holland to see the tulip fields.)
En 'Holanda', es común ver a la gente andar en bicicleta.
(In Holland, it's common to see people riding bicycles.)
Summary
While 'Países Bajos' is the correct and official term for the Netherlands in Spanish, 'Holanda' is commonly used in informal contexts. It's more accurate to use 'Países Bajos' when referring to the country as a whole, especially in formal or official situations.