Consent, as described by the Oxford Dictionary, is permission for something to happen or agreement to do something.
Consent applies to many stuff, not just sexual advances. From letting someone borrow your pen, to drinking tea, to hugs. I will be using the tea comparison for this.
Consent does not simply mean "both parties love each other". One can love someone but not consent to certain stuff, or may consent to stuff with those they don't particularly care for on an emotional level. If you ask someone if they want tea, and they say "Hell yeah, I love tea!" then great, that is active consent. They do indeed want tea. If they respond with "I'm not sure, maybe?" then you can still make that cup of tea if you want to, but don't be mad if they don't drink it when you offer it to them. And if they don't drink it, don't make them drink it. Just because you made it doesn't mean you are entitled to have them drink it.
If they respond "No, I don't want tea." then don't make them tea at all. Don't be mad at them for not wanting tea, don't annoy them until they give you until they tell you "Fine I want tea". That is coercion and it doesn't change their actual mind about whether they want tea or not. It is not consent.
If they say "yes, sure! thank you." but when the tea arrives they don't actually want the tea, don't make them drink it. They may have changed their mind. Sure it can be annoying because you went through all that effort to make them tea, but they still have no obligation to drink the tea just because of that. They did want tea, now they don't. It's okay for people to change their minds, don't make them feel guilty of that.
If they decide while drinking that they actually don't want tea, then don't make them drink the rest of it. Again, it's okay for people to change their minds, do not make them feel guilty of that. And if they're unconscious, then don't make them tea at all. Unconscious people can't answer the question "Do you want tea?". You may have asked them when they were conscious and they may have agreed, but now they're unconscious. make sure they're safe, and, this is important, don't make them drink the tea. They may have agreed then, sure, but unconscious people don't want tea.* If they were conscious when they started drinking it but then passed out, don't make them drink the rest of the tea.*
If they're not in the right mind, say, mentally unwell, then don't offer them tea at all, even if they say they want it or deserve it. They need safety, and comfort, not tea. You can offer later when they feel better. If they said yes to tea once, don't expect tea time always forever whenever you want. Don't come up to them unexpectedly and make them drink tea saying "But you wanted tea once!". Just because they wanted tea one day doesn't mean they want it anytime forever.
For both parties involved:
Are they actively saying "yes, I want it"?
Do they know to the fullest extent what they're in for? What they're agreeing to?
Are they allowed to change their mind at any given time and have it be respected by the other party?
Is there safety precautions? (such as safe words)
Are they on an equal level with no power imbalance that could put either party in jeopardy should they change their minds or say no
If the answer to all of these is yes, great! That falls under consent. If the answer to any of these is "no" or "maybe" then that is not consensual.
*Some points in the first part are more nuanced, like in the case of a contract for example. In such a case, if everything in the contract fits in the checklist above, awesome!