Full-size spares are interchangeable with your regular tires. Same size, same brand ideally. You can drive on a full-size spare indefinitely. Pickup trucks and many SUVs come with full-size spares.
Temporary spares (commonly called donuts) are rated for 50 miles maximum at 50 MPH or less. They have a higher pressure rating (typically 60 PSI) and a smaller diameter. Get to a tire shop fast.
Inflator kits (sealant + compressor) are increasingly common in new cars. They work for small punctures only — sidewall damage or large holes defeat them. Once you use the sealant, the tire usually needs replacement (the sealant ruins it for normal repair).
No-spare vehicles rely on run-flats or inflator kits. Some Tesla models, certain BMW and Mini configurations, and many electric vehicles ship without spares.
If you do off-road or long-distance driving frequently, a full-size matching spare is worth the trunk space.