I'm reading an interview in a magazine and one sentence says 'y cuando digo bueno, quiero decir que me guste.' I haven't learnt anything about the imperativo, but I believe 'me guste' is imperativo afirmativo. what is the significance of saying 'me guste' in this sentence and also what is the imperativo for generally?
guste is the present tense, subjunctive mood form of of gustar. (either 1st or 3rd person, singular)
The present tense, subjunctive endings are also used to form the imperative mood verb endings. (formally, and negatively) The imperative mood is used for creating commands.
In your example, guste is in the subjunctive mood and not the imperative mood. For a precise translation we might need more context to be exact, but one interpretation would be:
When I say "bueno", I want to say (I mean) that "I like it".