The universe is teeming with all sorts of extrasolar planets. Some of them are https://interestingengineering.com/what-is-a-rogue-planet">wandering through space alone, on the outskirts of the galaxy, with no Sun of their own to call "home." Others belong to planetary systems that are extremely different from our own. Some orbit multiple stars; others are in binary systems, and some aren't planets at all, but moons that may be habitable for a number of reasons.
One factor astronomers must consider before deeming a planet potentially "habitable" or "Earth-like" is through analyzing its characteristics, the characteristics of its star, and any other information that's possible to glean from the planet as it transits its sun. Some of this information can be used to determine if the planet lies in a goldilocks-zone, where life is theoretically possible, and whether it orbits its star from such a close distance that the two are tidally-locked.
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