iserith
Magic Wordsmith
If I had to summarize the concept of exploration, I would say "non-social investigation and problem-solving".
There is a very distinctive feeling about the exploration phase of an adventure: it's an out-of-character conversation between the players asking questions and the DM providing answers, then players making decisions and the DM describing the outcome.
The focus is not on the rules but on narrative descriptions. Rules kick in more or less often depending on DM's style, but they are not usually the starting point; even in a game where players think heavily in rules terms (i.e. they constantly go "I will make a check to search for traps", "I use my ability X to do Y") the overall feel is free-form and unstructured description. This is very different from combat, when almost every player starts thinking in terms of the structured rules framework.
Investigation and interaction are non-social and therefore mostly out-of-characters, even if descriptions are of course given by the DM through the eyes and ears of the PCs. So for instance, the players are not thinking in terms of language as being used by their PC in first person (as they would during the social interaction phase), but they are using language to ask questions / state intents directly to the DM and therefore just as they would do IRL.
Overall they are 3 quite different ways of thinking!
That said, just because the authors have summarized the game as being based on these 3 pillars, this does not mean we have to worry about fitting every single thing that happens at the gaming table into one and only one of those :/
While what you describe appears pretty common to me, it's not something that is fostered at my table. Exploration, combat, and social interaction are all done by the players describing what they want to do as per the basic conversation of the game (a statement of goal and approach). Questions of the DM are unwelcome. I discourage them by (1) striving to be clear and succinct in my descriptions and (2) encouraging players to do stuff in order to find out what they want to know. Excepting the players not hearing or understanding what the DM is saying, a question can actually be a form of purposeful failure mitigation on their part which goes outside the bounds of the game. A statement of action carries with it the possibility of consequence. Your character is doing something and you might have to roll dice to see what happens or something else undesirable occurs. But with questions, you can just have a little Q&A session with the DM without any risk to get what you need, bypassing any true exploration of the game world.
In my games, you state what you want to do and what you hope to accomplish. Then we go to the mechanics as necessary. There is more of an expectation of mechanics to come into play during combat than the other two pillars and initiative makes it a bit less free-form; however, the basic conversation of the game remains consistent.