According to Jesus at least, doesn’t simply mean living forever, on into eternity. Nor does it simply mean existing in a blissful, pain-free state. Those may very well be true. I suspect that they are.
For the record, by “eternal life” Jesus also does not mean going on to live in some sort of disembodied, floating-in-the-ether, angel-like state. No. There is something about embodied existence that is good and that will forever be a part of “eternal life.”
According to Jesus—in some of his plainest speech, without metaphor or hyperbole—”eternal life” means knowing God. It means being connected with the Life that has existed from eternity past, exists in the present moment, and will exist on into eternity future. Not knowing about God, but an intimate, relational, first-hand knowing. Stepping into such intimacy with the very source of Life changes one’s life.
Jesus also qualifies this statement by saying the only true God. There are, surprisingly, many gods. The Bible, as a whole, is actually far more polytheistic than we like to think. The goal of Jesus (as well as much of the rest of the Bible) is actually not to make anyone into good monotheists, but to whittle the myriad of available options down to only One worth believing in and worshiping and giving one’s life to.
The invitation to know these other gods comes with all kinds of promises of life. Empty promises. Fleeting promises. Half-baked promises. They are all, indeed, lesser gods who offer lesser life.