“Actually” is an adverb, and it is usually used for emphasis. It means “en realidad”. Consider these examples:
- Mr. Corbyn is actually not very intelligent (…en realidad/realmente no es muy inteligente). You could also write “Mr. Corbyn is really not very intelligent”.
- Unemployment in Spain has actually fallen (…el paro en España de hecho ha bajado). You could say “has fallen” and the meaning is the same. “Actually” just gives emphasis.
Sometimes “actually” is used to clarify a point or correcting a point. Consider these:
- That is not true (eso no es cierto), actually. Mr Podemos earns 100,000 a year not 50,000.
- Actually, Mrs. May is right about Brexit (de hecho, Senora May tiene razón).
- Mr. Morales went fishing yesterday and he told me “I actually caught a fish”. This suggests that he was not expecting to catch a fish.
- What did Mr. Trump actually (exactamente) say to Mr. Putin? Or better: What exactly did Mr. Trump say to Mr. Putin.
You can also say “in actuality” (en realidad), “actuality” being a noun.