Good on you for asking!
So it is about being spiritually "alive" - that is, to not only have a knowledge of the carnal reality, but also to know the spiritual reality. That makes you ask "what is spirit"?
Jesus said "God is spirit" and "those who worship Him must worship in spirit and in truth". By saying that, He is making a distinction between those who don't worship Him in spirit and in truth - they worship in some other way: "the futility of their thinking". They use their intellect to compute answers to the questions they get when they talk religion, but they haven't yet drank of the "living water" that Jesus says "if anyone drinks of the water I give them, it will become in them a fountain overflowing with life".
Jesus also says "it is the spirit that gives life, the flesh (self/ego/pride/mind etc) profits nothing. The words I have spoken to you, they are spirit and they are life".
So it is through words that the spirit can go into us and become that fountain of life. Jesus also said "you have been made clean by the word I have spoken to you, now remain in me so that you may produce fruit". In saying that, He shows that the ones who are "in Christ" (therefore they have been given the new life), have been "made clean" by the words He spoke.
What does that imply? .. only that the way we think is "dirty", "polluted" or "corrupted" and in need of cleansing by the words that give life.
Jesus said "you are my disciples if you keep my word, and you will know the truth and the truth will set you free" - so He is saying that the corrupted thinking is a thing that takes us captive, and that we can only be set free of it by coming to know the truth. Furthermore, He promises that if we keep His commandments, then we will come to know the truth.
It's interesting to see a detail of what Jesus said to Nicodemus: "unless a man is born again, he cannot SEE the kingdom of God". In other words, the kingdom of God is "in our midst" and it is a thing that can be seen, but only after we have been made alive in the spirit (aka: made clean by the Word of life).
So the Word of life is really important, and it is a thing that, evidently, not every person has.
Proverbs 18:21 says that the tongue has the power to give life and death (when we speak in terms of spiritual life and spiritual death). So there is a lot of people in this world who are not born-again: they do not perceive the kingdom of God (consider 1 Corinthians 2:14-16). Their words do not have the power to give life, because they don't know life (although, Jesus is able to speak through them and you will know that when you meet Him - but their faith is a blind faith. They do not "see" the kingdom of God).
So, ultimately, it is a thing that you cannot just go out there and get. It is a thing I cannot just give to you. But just as St. Paul said to the Greeks in Acts 17:27 : "they were to search around for Him and perhaps grope around for Him and find Him. Yet, He is not far from each one of us".
So that's what we are talking about: it is your thinking that has fallen into spiritual death through the corruption of the words of the ones who are spiritually dead - having been "lured by your desires into sin, and sin having come to maturity, bringing forth death" (James 1:14-15).
But Jesus is faithful, and through His work in the cross, He has made a way for us to be redeemed from the adversary who took us captive, so He continues to operate through us (when we purify ourselves to make ourselves fit vessels for His Holy Spirit, He is able to speak the words of life through us).
So as you go day by day, some of our words will be building your mind into His vision for your redemption and one day He will say just the right words to you that "the lights will go on", "a penny will drop", "the seed will take root" etc, and that is the new life (1 Corinthians 3:6-7). No longer will you be the one who is on the outside asking for His living water, but you will be on the inside sharing His water with others.
Now, what's important to remember when that happens, is the parable of the sower, through Matthew 13: the seed that we sow, it can grow, but it also can be snatched away. So that is why Jesus told the parable of the "pearl of great price", that when he had found the precious pearl, he hid it in a field and went and sold everything that he had, and bought the field.
If you like to stay in that sort of life-giving word, there is this booklet that I share with people:
www.adonai-reigns.life/the-gospel, and most of that is text from the bible. As you go from page to page, thinking about what the bible is saying about each topic, the mind is brought to a place of awareness, and some people will keep following Him, while others will rather go back to their former life (because not everyone truly does want to be Christian).
Nice to meet you today!