Much like in other large countries, depending where you travel to you'll find different types of cuisine: inland, coastal, mountainous... each one having its ingredients and traditions, which makes for a diverse culinary experience.
Furthermore, Spain is not a "country" in the strict sense but a patchwork of very different cultures -each with different sociological and historical backgrounds-, which offers even a much more diverse cuisine. In fact, there isn't a "Spanish cuisine" as such, but a Basque cuisine, a Catalan (or Mediterranean if you like, as it embraces territories beyond Catalonia) cuisine, etc. Those areas that have no seacoast (ie Castille or Extremadura) and thus have harsher climates, tend to have traditional dishes that include lots of lard, oil, and meats... while those with moderate climates -normally along the coast- include a wider variety of ingredients, especially vegetables, fruits and also seafood and fish. Needless to say that bordering cultures have "similar" dishes that transcend their political or administrative borders.
And to top it up, food is an essential pillar of the different cultures in the Iberian peninsula, not only it's meant to feed hunger but also it's often the motive of social gatherings, therefore "eating out" has a different meaning than in other countries. This is common in countries with mild climates, where the population spend a great deal of time outdoors. This "way of life" has positioned food at the centre of society and has evolved in an extensive offer, from simple everyday dishes to sophisticated haute-cuisine. Spain has 228 Michelin-starred restaurants (as of 2022), being Catalonia the area with the most starred restaurants (49) and a few of the top restaurants in the world, according to The World's Best 50 Restaurants produced by UK media company William Reed.
In short, you'll encounter a wide variety of offers regarding food... you just have to peruse a bit.
If you happen to visit my turf, Catalonia, here there is an introduction to our cuisine: https://cmsmultimedia.catalunya.com/mds/multimedia/485418/