It's common for people to describe themselves as "spiritual but not religious". What do you suppose that means?
It might mean that they think its likely that there's some sort of spiritual "stuff" that exists, and that the physical universe isn't all there is. But they don't take it much further than that.
It might also mean that a person has rejected, to some extent at least, the explanations offered by the familiar religions - Christianity, Islam, Buddhism, Hinduism, Chinese traditional religion, etc.
It might be more of a rejection of ritual - of attending regular services, or of observing certain practices - than it is a rejection of a thought-structure.
It might mean that someone has thought deeply, and explored hard, and hasn't yet found an organization, or an organized body of thought, that is convincing.
Or, it could just mean that someone hasn't thought much about it, but thinks that it sounds "deep" to say it.
Let's take a close look. The word "religion" may come from the Latin word "religare", which means to bind or connect, or to have an obligation to. It's also possible that it comes instead from the Latin "relegere", meaning to heed, or have a care for. They aren't dissimilar origins; in both, there is a connotation of commitment. (Here's a link to an article about the etymology).
Constructively, religion can be a commitment to learning truth, and trying to be good, and of connecting with the spiritual love and wisdom of God. So can spirituality. Religion might imply more structure, and more of an active approach, in learning and practicing. Spirituality sounds a little looser, and a little bit more passive, but there's still an appreciation for higher things, and an openness to influx.
External ritual and observance can be empty if they lack internal love to the Lord and the neighbor. That doesn't necessarily mean that they're useless; sometimes you need to "fake it till you make it". You're going through the motions, but even that fairly empty action can make space for genuine love and wisdom to flow in. But if they're empty, and just being done to look good -- they can stay empty. On the other hand, though, they can be full, too... full of love, and deep thought and emotion, creating space and time for seeking God's love and wisdom.
There's a memorable parable in Luke 18:10-14...
"Two men went up into the temple to pray; the one a Pharisee, and the other a publican.
The Pharisee stood and prayed thus with himself, 'God, I thank thee, that I am not as other men are, extortioners, unjust, adulterers, or even as this publican. I fast twice in the week, I give tithes of all that I possess.'
And the publican, standing afar off, would not lift up so much as his eyes unto heaven, but smote upon his breast, saying, 'God be merciful to me a sinner.'
I tell you, this man went down to his house justified rather than the other: for every one that exalteth himself shall be abased; and he that humbleth himself shall be exalted."
For sure, the people in any given church aren't going to be perfect; they're hopefully trying to be good - trying to love God and the neighbor, but are there going to be failings and flaws? Yes. But, professions of spirituality are also empty, if there's no effort to learn truth and actively shun evils as sins.
At bottom, religion and spirituality may not really be very different. They are the way that human beings try to figure out what's true, and what's good, and then to start living better lives.
